taxonID	type	description	language	source
038687FCFF93A75A3AF105BEFBE2758E.taxon	diagnosis	Diagnosis (taken from Peña Cantero et al., 1997). Feather-like, colonial hydroids with branched or unbranched stem, divided into internodes or undivided, mono- or polysiphonic and with two longitudinal rows of apophyses, alternately arranged in one plane and supporting hydrocladia. Apophyses with varied number of nematophores on upper surface near axil with hydrocaulus, emerging through a raised, perforated part of the periderm (‘ mamelon’) and / or through simple holes in the perisarc. Stem without nematophores or nematothecae. Hydrocladia typically branched. Degree of branching varied, fourth-order hydrocladia having been recorded. Hydrocladia homomerously divided into internodes (with the exception of Oswaldella herwigi El Beshbeeshy, 1991) bearing one hydrotheca and two nematophores each: one mesial superior nematophore and another mesial inferior. First nematophore placed behind free adcauline hydrothecal wall; second situated below hydrotheca at a more or less distinct elevation of internode. Mesial inferior nematophore with or without rudimentary, scale-shaped nematotheca. Hydrothecae cupshaped to tubular. Colonies dioecious, with sexual dimorphism. Gonothecae inserting on hydrocladia below hydrotheca next to mesial inferior nematophore. Cnidome composed of microbasic mastigophores, typically in two size classes. List of species described in or now referred to Oswaldella	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF93A75A3AF105BEFBE2758E.taxon	description	Oswaldella monomammillata sp. nov.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF9CA75E3A4205FAFD757708.taxon	discussion	Remarks. Oswaldella antarctica is well characterized by the monosiphonic and unbranched stems, divided into internodes, the presence of two axillary nematophores and one ‘ mamelon’ on the cauline apophyses, the much branched hydrocladia, the presence of a much reduced nematotheca on the hydrocladial internodes and the shape of the hydrotheca which is situated on the middle of the hydrocladial internode (table 1). Ecology and distribution. Oswaldella antarctica is known from off Seymour Island (Graham Land), where it was collected at 150 m depth (Jäderholm, 1904; Peña Cantero and Vervoort, 1995).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF98A75C3A3B074CFCA0752E.taxon	description	(figure 1)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF98A75C3A3B074CFCA0752E.taxon	materials_examined	Material examined. 27 / 1924, one stem ca 40 mm high (USNM 1003297); 27 / 1951, one fragmented stem (largest fragment ca 20 mm long) (USNM 1003298); 32 / 1995, several stem fragments up to 20 mm long, with gonothecae (USNM 1003299; RMNH-Coel. 30201); 32 / 1996, three stem fragments up to 17 mm long (USNM 1003300); 32 / 2021, two stem fragments up to 5 mm long in bad condition (USNM 1003301); 32 / 2095, numerous stems up to 60 mm high, with gonothecae (USNM 1003302; RMNH-Coel. 30202; MNCN 2.03 / 230); 32 / 2128, three fragments and stems up to 42 mm high (USNM 1003303). Description. Colonies composed of monosiphonic, unbranched (occasionally branched) stems up to 60 mm high. Stem divided into internodes with one or two apophyses per internode, slightly geniculate. Apophyses alternately arranged in one plane, forming two longitudinal series, slightly directed upwards, forming an angle of ca 70 – 80 °. Cauline apophyses usually provided with one, sometimes two (27 / 1924, 32 / 2095, 32 / 1996 in part), axillary nematophores, but deprived of ‘ mamelons’ (figure 1 A – C). Cauline apophyses supporting hydrocladia (figure 1 A), usually without node in between (present in 27 / 1924). Hydrocladia up to fourth order present. Hydrocladial branching symmetrical (figure 1 A): first hydrocladial internode bifurcated, with two prongs of equal development (figure 1 B, C), and giving rise to two secondary hydrocladia, each one with some third-order hydrocladia. These, occasionally, forming fourth-order hydrocladia. Hydrocladia basally following angle of cauline apophyses, but distally curving strongly upwards. Hydrocladia homomerously divided into hydrothecate internodes, provided with one hydrotheca and two nematophores (figure 1 D – J): one mesial superior nematophore emerging through a perisarc hole situated at the end of adcauline hydrothecal wall and one mesial inferior nematophore emerging through a perisarc hole in a strongly marked elevation of internode (angle between long axis of hydrocladial internode and steep wall of infrathecal elevation usually ca 90 °, though sometimes less). Without mesial inferior nematotheca. Top of distal hydrocladial internodes pointed (figure 1 D, E, H). Hydrotheca low, placed on basal half or third of hydrocladial internode, adcauline wall fully adnate (figure 1 D – J). Rim either even, and then hydrothecal aperture circular, or uneven with frontally depressed hydrothecal aperture due to presence of two slightly raised lateral lobes. Immature gonothecae present, inserting close to mesial inferior nematophore. Gonotheca cone-shaped, distally truncated (figure 1 K). Remarks. Number of axillary nematophores on the cauline apophyses variable; even on the same stem we have observed apophyses bearing two and apophyses with a single axillary nematophore. There is a tendency, therefore, for the fusion of the two holes into one (figure 1 B, C). Ecology and distribution. Oswaldella bifurca is a deep-water species, having been found from 450 to 640 m depth (Peña Cantero et al., 1997); our material comes from 342 to 1610 m depth. It has been found with gonothecae in November (Hartlaub, 1904) and February (Peña Cantero et al., 1997); our colonies with immature gonothecae were found in January and February. It is used as a substratum by other hydroids (Eudendrium sp., Filellum sp.). Hitherto Oswaldella bifurca was only known from West Antarctica, being recorded at 70 ° 20 ∞ S – 83 ° 23 ∞ W, in the Bellingshausen Sea (Hartlaub, 1904), and off the south coast of the Weddell Sea (Peña Cantero et al., 1997). Our material, however, comes from East Antarctica, where it was found at the central basin of the Ross Sea and off Victoria Land [Pennell Bank, east of Cape Hallett, off Cape Adare and off Buckle Island (Balleny Islands)].	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF9AA7423A110559FCD175EF.taxon	description	(figure 2)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF9AA7423A110559FCD175EF.taxon	materials_examined	Material examined. 0000 X, two stems up to 75 mm high, with immature gonothecae (USNM 1003304; RMNH-Coel. 30203); 000 AM, several fragments up to 35 mm long (USNM 1003305; RMNH-Coel. 30204); 002 / 002, two stems up to 90 mm high (USNM 1003306; RMNH-Coel. 30205). Description. Colonies consisting of monosiphonic and unbranched stems up to 90 mm high, occasionally with some stolonal tubes. Hydrocaulus provided with apophyses alternately arranged in one plane and in two longitudinal rows. Cauline apophyses directed upwards, forming an angle of ca 45 °, or slightly larger, with long axis of stem, provided with two nematophores, each one emerging through an axillary perisarc hole (figure 2 B). Stems divided into internodes or with occasional internodes. Cauline apophyses supporting hydrocladia; secondary hydrocladia may be present (figure 2 A). Cauline apophyses and hydrocladia separated by distinct node. Hydrocladia homomerously divided into hydrothecate internodes provided with one hydrotheca and two nematophores (figure 2 C – H): one mesial superior, emerging through a simple perisarc hole situated behind free adcauline hydrothecal wall, and one mesial inferior nematophore emerging through a hole situated on an elevation of internode and provided with a scale-shaped nematotheca. Top of distal hydrocladial internodes truncated. Hydrotheca elongate, usually situated slightly above middle of internode (figure 2 C – H), sometimes slightly below that point; free part of adcauline wall considerable. Hydrothecal aperture circular or kidney-shaped and strongly tilted adcaudally. Abcauline wall of hydrotheca convex. Immature gonothecae present, originating just below mesial inferior nematophore, cone-shaped; greatest diameter at truncated top (figure 2 I). Ecology and distribution. Oswaldella billardi is a shelf species (Peña Cantero and Vervoort, 1997). It has been recorded from 7 (Stepan’yants, 1972) to 206 m depth (Naumov and Stepan’yants, 1962) on bottoms of small rocks with red algae (Briggs, 1938), sand and boulders (Naumov and Stepan’yants, 1972) and rocks, pebbles, sand and mud (Stepan’yants, 1979). Our material was collected from 238 to 412 m depth. It has been found with gonothecae in January (Briggs, 1938; Stepan’yants, 1979) and in November (Stepan’yants, 1979); our material with immature gonothecae was collected in December.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF84A7403A570212FE05752E.taxon	description	(figure 3)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF84A7403A570212FE05752E.taxon	materials_examined	Material examined. 32 / 1996, one stem ca 8 mm high (USNM 1003307). Description. Stem monosiphonic, unbranched (figure 3 A), provided with apophyses alternately arranged in two longitudinal rows. Stem divided into internodes each with one apophysis, internodes arranged in zigzag fashion; stem internodes with bifurcation at origin of cauline apophysis. Angle between long axis of cauline internode and apophyses wider than 45 °; angle between cauline apophyses and succeeding cauline internode ca 90 ° (figure 3 A). Cauline apophyses provided with two nematophores: one emerging through a hole in perisarc of axil (figure 3 B) and another nematophore emerging through a ‘ mamelon’ situated laterally on dorsal side of apophysis (figure 3 C). Distinct node present between cauline apophyses and hydrocladia (figure 3 C). Hydrocladia undivided or bifurcated (figure 3 A); up to secondary hydrocladia present; arrangement always symmetrical. Hydrocladia homomerous; all internodes hydrothecate; distal internodes apically truncated. Hydrocladial internodes provided with one hydrotheca and two nematophores (figure 3 B, D – G): one mesial superior emerging through a perisarc hole situated behind free portion of adcauline hydrothecal wall and one mesial inferior, deprived of nematotheca, emerging through a perisarc hole situated on a strongly marked elevation of internode (angle between long axis of hydrocladial internode and steep slope of infrathecal elevation almost 90 °). Hydrothecae placed on basal half or basal third of hydrocladial internodes (figure 3), shallow; aperture circular and either perpendicular to longitudinal axis of internode or slightly tilted downwards; rim even. Adcauline wall of hydrotheca with conspicuous free portion, abcauline wall straight, running smoothly into wall of internode; angle with long axis of internode ca 45 °. Gonothecae absent. Remarks. Oswaldella blanconae is a rare species, hitherto only recorded by Blanco (1984). It is a distinctive species, characterized by hydrotheca placed on basal half or third of the internode, the absence of mesial inferior nematothecae (although a nematophore is present), the shape of the hydrotheca, the presence of one ‘ mamelon’ besides the axillary nematophore on the cauline apophyses, and the arrangement of cauline internodes. Ecology and distribution. Oswaldella blanconae appears to have a circum-Antarctic distribution. The only previous record was from off Low Island, in West Antarctica, at a depth of 90 – 100 m (Blanco, 1984). Our material comes from east of Cape Hallett (Victoria Land), in the Ross Sea region, where was collected between 344 and 351 m depth.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF86A740399F0575FD75734C.taxon	materials_examined	Material examined. 6 / 428, Three stem fragments up to 35 mm long. Remarks. The material of this species was previously described and figured by Peña Cantero and Vervoort (1998). Oswaldella crassa is characterized by the absence of nematotheca in the hydrocladial internodes, the presence of two axillary nematophores and one ‘ mamelon’ on the cauline apophyses, the shape of the hydrotheca, situated on the middle of the hydrocladial internodes, the strong development of the perisarc, the absence of node between cauline apophyses and hydrocladia, and the absence of internodes in the stem (cf. table 1). Ecology and distribution. Oswaldella crassa is known only from the Bransfield Strait area, where it was collected at depths from 662 to 1120 m in January (Peña Cantero and Vervoort, 1998).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF86A741399A0393FD21774A.taxon	materials_examined	Material examined. 6 / 428, three stems up to 35 mm high. Remarks. The material of this species was previously described and figured by Peña Cantero and Vervoort (1998). Oswaldella curiosa is well characterized, especially by the shape of the hydrotheca, since it is the only known species of the genus with a completely abcaudally directed hydrothecal aperture. It is also characterized by the absence of mesial inferior nematothecae in the hydrocladial internodes, the absence of a node between cauline apophyses and hydrocladia, and by the presence of a single axillary nematophore in the cauline apophyses (cf. table 1). Ecology and distribution. Oswaldella curiosa is known only from the Bransfield Strait area, where it was collected at depths between 662 and 1120 m in January (Peña Cantero and Vervoort, 1998).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF87A74139D8078EFE3770CD.taxon	description	(figure 4)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF87A74139D8078EFE3770CD.taxon	materials_examined	Material examined. 001 / 011, two stems up to 60 mm high (USNM 1003308; RMNH-Coel. 30206);? 32 / 2068, two stems up to 24 mm high (USNM 1003309; RMNH-Coel. 30207). Description. Colonies composed of monosiphonic and unbranched stems up to 60 mm high. Hydrocaulus provided with apophyses alternately arranged in one plane, forming two longitudinal rows; apophyses upwardly directed, forming an angle of ca 45 ° with long axis of stem (figure 4 A). Hydrocaulus divided into internodes; usually one apophysis per internode. Cauline apophyses provided with a single axillary nematophore, emerging through a simple perisarc hole (figure 4 B, C). Apophyses supporting unbranched hydrocladia separated by a distinct node (figure 4 A, B). Hydrocladia homomerously divided into hydrothecate internodes provided with one hydrotheca and two nematophores (figure 4 B, D – H): one mesial superior, emerging through a perisarc hole situated behind free adcauline hydrothecal wall, and one mesial inferior springing from a perisarc hole in a slight elevation of internode and provided with a scale-shaped nematotheca. Distal hydrocladial internodes apically truncated. Hydrotheca elongate, placed on middle of hydrocladial internode (figure 4 B, D – H); distinct part of its adcauline wall free. Abcauline hydrothecal wall straight, though convex basally. Hydrothecal aperture circular, more or less perpendicular to long axis of internode; rim even. Gonothecae present in the material from Stn 32 / 2068 (figure 4 I), inserting on infrathecal elevation of hydrocladial internode, fusiform, provided with an almost circular, subterminal aperture; basal third with node or diaphragm. Remarks. The material from Stn 32 / 2068 differs from O. delicata studied so far by the absence of internodes in the stems, the presence of an inconspicuous node between the cauline apophyses and the hydrocladia (figure 4 B), and the shape of the gonothecae (figure 4 I). The difference in gonothecal structure may be due to sexual dimorphism. In the original description of O. delicata only one type of gonotheca was found; sexual dimorphism is known to exist in species of Oswaldella. Ecology and distribution. Oswaldella delicata was known only from 430 to 440 m depth off the south coast of the Weddell Sea, occurring on muddy bottom; colonies with gonothecae were collected in February (Peña Cantero et al., 1997). Our material was collected at 438 m depth, east of Cape Wheeler, off the south-west coast of the Weddell Sea.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF81A747391C06B5FCCB7467.taxon	discussion	Remarks. Oswaldella elongata is an uncommon species, well characterized by the long hydrothecae, the absence of mesial inferior nematothecae in the hydrocladial internodes, the presence of two axillary nematophores and two ‘ mamelons’ in the cauline apophyses and the presence of only secondary hydrocladia (cf. table 1). Ecology and distribution. Oswaldella elongata is known only from off Clerke Rocks and South Georgia, where it was found between 86 and 250 m depth, growing on hydrocorals (Peña Cantero et al., 1995).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF81A74739D6048CFCB470CD.taxon	description	(figure 5) Oswaldella encarnae Peña Cantero et al., 1997: 356 – 358, figures 4, 13 D; Peña Cantero and García Carrascosa, 1998: 179; 1999: 214; Peña Cantero and Vervoort, 1998: 36; Peña Cantero and Marques, 1999: 85. Material examined. 002 / 009, three fragments and stems up to 48 mm high (USNM 1003310; RMNH-Coel. 30208). Description. Monosiphonic and unbranched stems up to 48 mm high. Hydrocaulus provided with cauline apophyses directed upwards and forming an angle of ca 45 ° with long axis of stem (figure 5 A). This stem divided into internodes with one or two apophyses per internode. Cauline apophyses provided with two axillary nematophores, emerging through simple perisarc holes (figure 5 B, C); without ‘ mamelons’. Each apophysis supporting an unbranched hydrocladium (figure 5 A – C), separated by a distinct node (figure 5 B, C); top of distal hydrocladial internodes truncated. Hydrocladia homomerously divided into internodes each provided with one hydrotheca and two nematophores (figure 5 B – G): one infrathecal mesial nematophore with a scale-shaped nematotheca and situated on a slight elevation of internode, and one mesial superior nematophore, emerging through a perisarc hole placed behind free adcauline hydrothecal wall. Hydrothecae usually placed on distal half of internodes (figure 5); sometimes in the middle (usually in basalmost internodes). Hydrotheca shallow, with part of the adcauline hydrothecal wall free. Abcauline wall straight, running smoothly into wall of internode under an angle of ca 30 ° with internodal long axis. Aperture circular, slightly tilted downwards; rim even. Gonothecae absent. Ecology and distribution. Oswaldella encarnae appears to be a shelf species, having been found from depths of 400 to 440 m on muddy bottoms (Peña Cantero et al., 1997); our material was found at a depth of 252 m. Peña Cantero et al. (1997) recorded gonothecae from February. Presently Oswaldella encarnae can best be considered endemic to the Weddell Sea, in West Antarctica, as it has been reported off the south and east coasts of the Weddell Sea (Peña Cantero et al., 1997). We record it here from north off Berkner Island, off the south coast of the Weddell Sea.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF83A748399106B5FB5875B4.taxon	description	(figures 6, 7)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF83A748399106B5FB5875B4.taxon	materials_examined	Material examined.? 001 / 011, one stem ca 70 mm high (USNM 1003311); 12 / 1001, one stem ca 10 mm high (USNM 1003312); 12 / 1002, one fragmented stem (largest fragment ca 55 mm long) (USNM 1003313); 12 / 1003, numerous stems up to 65 mm high, with gonothecae (USNM 1003314; RMNH-Coel. 30209; MNCN 2.03 / 231); 575 / 061, three stem fragments up to 35 mm long (USNM 1003315); 691 / 003, one stem fragment ca 55 mm long, with gonothecae (USNM 1003316); 691 / 020, one stem ca 62 mm high (USNM 1003317); 702 / 511, one distally broken stem ca 30 mm high (USNM 1003318);? 721 / 1070, two stems up to 80 mm high, with gonothecae (USNM 1003319; RMNH-Coel. 30210); 721 / 765, three stems up to 65 mm high, with gonothecae (USNM 1003320; RMNH-Coel. 30211; MNCN 2.03 / 232); 731 / 1756, one fragment ca 23 mm long (USNM 1003321); 824 / 041 - 1, one stem ca 23 mm high (USNM 1003322); 833 / 018 - 1, one stem ca 130 mm high (USNM 1003323); SOSC-L 26, two stems up to 30 mm high (USNM 1003324). Description. Colonies consisting of monosiphonic and unbranched stems up to 130 mm high. Stems typically robust, with strongly developed perisarc (figure 6 A – E). Hydrocaulus provided with apophyses alternately arranged in one plane, forming two longitudinal rows. Cauline apophyses directed upwards, forming an angle of ca 70 ° with long axis of stem, provided with two nematophores, each emerging through an axillary perisarc hole (figures 6 B, 7 B). Stems with occasional nodes or completely without. Cauline apophyses supporting hydrocladia (figures 6 A, 7 A); up to thirdorder hydrocladia present (figure 6 A). Node between cauline apophyses and hydrocladia absent (figure 6 B), indistinct or present in smallest stems with little developed perisarc (figure 7 B). Hydrocladia homomerously divided into hydrothecate internodes each with one hydrotheca and two nematophores (figures 6 C – E, 7 C – J): one mesial superior, emerging through a simple perisarc hole behind free adcauline hydrothecal wall, and one mesial inferior nematophore emerging through a hole on an elevation of internode and provided with a scale-shaped nematotheca. Top of distal hydrocladial internodes truncated. Hydrotheca elongate, usually situated in middle of internode (figures 6, 7); sometimes, mainly in proximal part of hydrocladia, on distal half; part of adcauline wall of hydrotheca free. Aperture kidney-shaped and strongly tilted adcaudally. Abcauline wall of hydrotheca basally straight, strongly curving inwards distally. Female gonothecae present, inserting just below mesial inferior nematophore, fusiform (figure 6 A, F); aperture circular and subterminal. Gonotheca sometimes provided with node or diaphragm at basal fourth. Remarks. Oswaldella erratum is allied to O. billardi, sharing many features (cf. table 1). They can be distinguished by the larger size of the hydrothecae in O. billardi, in which the length of the abcauline hydrothecal wall may be 350 M m at the first hydrocladial internode and may reach 400 M m at the last. In O. erratum that length may be 240 M m at the first hydrocladial internode, reaching up to 360 M m in the last internodes. Moreover, in O. billardi the hydrocladia are always separated from the cauline apophyses by a distinct node, whereas in O. erratum that node is usually absent or little marked. In O. erratum, the stem is deprived of nodes or has only occasional internodes, whereas in O. billardi the stem usually presents internodes. In O. billardi only secondary hydrocladia are present, whereas in O. erratum there are typically up to third-order hydrocladia. Ecology and distribution. Oswaldella erratum is a shelf species (Peña Cantero et al., 1997), having been found at depths from 70 (Billard, 1914) to 696 m (Peña Cantero et al., 1997) on bottoms of mud and sand (Broch, 1948), mud and pebbles (Billard, 1914), and on rocky and stony bottoms (Peña Cantero et al., 1997). Our material comes from depths of 55 to 311 m and was found on gravel. It has been found with gonothecae in March (Peña Cantero et al., 1997) and in November (Billard, 1914); we found fertile colonies in January, February and March.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF8EA74E3A0D05F0FE0070CD.taxon	description	(figure 8; table 2) Material examined. 691 / 26, one stem ca 75 mm high (holotype, USNM 1003325); 721 / 1063, three stem fragments up to 50 mm high (USNM 1003326; RMNH-Coel. 30212; MNCN 2.03 / 233). Description. Colonies consisting of monosiphonic and unbranched stems up to 75 mm high. Hydrocaulus provided with apophyses alternately arranged in one plane and forming two longitudinal series. Cauline apophyses directed upwards, forming an angle of ca 45 ° with long axis of stem. Stem divided into internodes with usually one or two apophyses per internode although up to four apophyses have been observed. Cauline apophyses with three (figure 8 C), occasionally four (figure 8 B) nematophores: two axillary nematophores, each one emerging through a simple perisarc hole, and one more emerging through a ‘ mamelon’. Occasionally an extra nematophore is present, emerging through a second ‘ mamelon’. Cauline apophyses supporting hydrocladia with asymmetrical branching (figure 8 A). First hydocladial internode bifurcated, giving rise to two unequally developed prongs, this process being repeated at the next internodes; ramifications all in one plane. Cauline apophyses and hydrocladia separated by a distinct node (figure 8 A, B). Hydrocladia homomerously divided into hydrothecate internodes, each provided with one hydrotheca and two nematophores (figure 8 D – K): one mesial superior nematophore, emerging through a simple perisarc hole situated behind free adcauline hydrothecal wall, and one mesial inferior nematophore emerging through a hole Hydrothecae Length of abcauline wall 80 – 120 Length of free part of adcauline wall 20 – 30 Diameter at rim 130 – 150 Internode Length 680 – 730 Diameter under hydrotheca 150 – 170 situated on a strong elevation of the internode and deprived of any kind of nematotheca. Top of distal hydrocladial internodes truncated. Hydrotheca shallow, placed on proximal half of internode or in the middle (figure 8 D – K). Hydrothecal aperture frontally depressed; rim uneven due to the presence of two strongly developed lateral lobes. Hydrotheca provided with a conspicuous free portion of its adcauline wall. Gonothecae absent. Remarks. Oswaldella frigida sp. nov. is allied to O. bifurca in general appearance, but differs in many respects (cf. table 1). In O. bifurca there is usually a single nematophore on the cauline apophyses emerging through a simple axillary perisarc hole (occasionally two), in O. frigida sp. nov. there are typically four nematophores on the cauline apophyses, two axillary nematophores emerging each from a perisarc hole and two more emerging each from a ‘ mamelon’ (occasionally only a single ‘ mamelon’). Also, though in both species the hydrotheca is frontally depressed, in O. frigida sp. nov. that frontal depression is much better developed; in fact, in many hydrothecae of O. bifurca the rim is even. Moreover, whereas in O. bifurca the hydrotheca is adnate over the entire adcauline wall, that adcauline hydrothecal wall usually has a distinct free portion in O. frigida sp. nov. In O. bifurca, the top of the distal hydrocladial internodes is pointed, whereas in O. frigida sp. nov. that part is truncated. In O. bifurca the hydrocladial arrangement is usually symmetrical, but in O. frigida sp. nov. that disposition is asymmetrical. In O. bifurca the first hydrocladial internode is distinctly bifurcated, giving rise to two secondary prongs of equal development, while in O. frigida sp. nov. that first internode gives rise to two unequally developed prongs that could be seen as the first-order hydrocladium giving rise to several secondary hydrocladia. In O. bifurca the cauline apophyses form an angle of ca 70 ° with the long axis of the stem, whereas in O. frigida sp. nov. that angle is ca 45 °. In O. frigida sp. nov. there is a distinct node separating cauline apophyses and hydrocladia; such a node is absent in O. bifurca, only in the youngest stems is it possible to find an indistinctly indicated node. In O. bifurca the stem is slightly geniculate, due to the arrangement and structure of the cauline apophyses, whereas in O. frigida sp. nov. the stem is straight. Finally, in O. bifurca the hydrocladia proximally follow the angle of ca 70 ° of the cauline apophyses, curving strongly upwards distally, whereas in O. frigida sp. nov. the hydrocladia completely follow the angle of ca 45 ° of the cauline apophyses. Ecology and distribution. Oswaldella frigida sp. nov. has been collected from depths of 44 to 124 m off Low Island and off Nelson Island, in the South Shetland Islands. Etymology. The specific name frigida refers to the frigid conditions under which this species lives.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF89A74F390706B5FE3175DD.taxon	discussion	Remarks. Oswaldella garciacarrascosai is well characterized by the absence of mesial inferior nematothecae in the hydrocladial internodes, the presence of two axillary nematophores and one ‘ mamelon’ in the cauline apophyses, the shape of the hydrotheca, and the presence of only secondary hydrocladia (cf. table 1). Ecology and distribution. Oswaldella garciacarrascosai was found from depths of 330 to 340 m on muddy bottoms off the south coast of the Weddell Sea. It was observed epibiotic on Bryozoa; fertile colonies were found in January and February (Peña Cantero et al., 1997).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF89A74F390706B5FE3175DD.taxon	description	Cantero and Marques, 1999: 85. Remarks. Oswaldella gracilis is an uncommon species, characterized mainly by the shape of the hydrotheca, which is low and laterally depressed, the absence of mesial inferior nematothecae in the hydrocladial internodes, the presence of a single axillary nematophore in the cauline apophyses, and the presence of only first-order hydrocladia (cf. table 1). Ecology and distribution. Oswaldella gracilis is known from off the south coast of the Weddell Sea, where it was collected at a depth of 440 m (Peña Cantero et al., 1997).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF89A74D39DF0201FE6B729D.taxon	description	(figure 9)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF89A74D39DF0201FE6B729D.taxon	materials_examined	Material examined. 702 / 464, one stem ca 145 mm high (USNM 1003327); 702 / 465, two stems up to 500 mm high (USNM 1003328; RMNH-Coel. 30213); 721 / 776, four stems up to 460 mm high, with gonothecae (USNM 1003329; RMNH-Coel. 30214; MNCN 2.03 / 234). Description. Colonies consisting of polysiphonic and unbranched stems up to 500 mm high. Hydrocaulus divided into internodes, occasionally so in Stn 702 / 465, and provided with alternately arranged apophyses, forming two longitudinal rows in one plane. Cauline apophyses directed upwards, forming an angle of ca 45 ° with long axis of stem and provided with four nematophores (figure 9 B): two axillary nematophores emerging through simple perisarc holes and two more emerging each through a ‘ mamelon’, placed laterally on upper surface of apophysis. Cauline apophyses supporting branched hydrocladia; up to third-order hydrocladia observed (figure 9 A). Hydrocladial arrangement symmetrical (figure 9 A); first hydrocladial internode giving rise to two secondary hydrocladia that usually support two or more third-order hydrocladia. No distinct node between cauline apophyses and hydrocladia, although present in the material from Stn 702 / 465. Top of distal hydrocladial internodes truncated. Hydrocladia homomerously divided into hydrothecate internodes, each provided with one hydrotheca and two nematophores (figure 9 C – F): one mesial superior emerging through a perisarc hole situated behind free adcauline hydrothecal wall and one mesial inferior provided with a much-reduced nematotheca and emerging through a perisarc hole situated on a slight elevation of internode. Hydrotheca shallow, situated on distal half of internode (figure 9 C – F). Adcauline hydrothecal wall almost completely adnate; aperture circular and approximately perpendicular to long axis of internode; rim even. Abcauline hydrothecal wall straight; angle with internodal long axis very acute. Female gonothecae present (figure 9 G), inserting on infrathecal elevation of hydrocladial internodes, large, club-shaped and provided with a subterminal aperture. Remarks. Oswaldella grandis is a well-characterized species, easily recognizable by the large, unbranched stems, the shape of the hydrotheca which is placed on the distal half of the hydrocladial internodes, the much-reduced nematotheca, the shape of the gonothecae and the presence of four nematophores on the cauline apophyses, two of which emerge through ‘ mamelons’ (cf. table 1). Ecology and distribution. Oswaldella grandis appears to be a shelf species, having been found at depths of 220 to 440 m on muddy bottoms and on bottoms with small stones (Peña Cantero et al., 1997); our material comes from 109 to 154 m. It is used as a substratum by other hydroids (Billardia sp.) (Peña Cantero et al., 1997). It has been collected with gonothecae in January and February (Peña Cantero et al., 1997); our fertile material was found in January. Oswaldella grandis seems to be endemic to West Antarctica (Peña Cantero and Vervoort, 1998). It is known from off Elephant Island (Peña Cantero and García Carrascosa, 1995) and off the south coast of the Weddell Sea (Peña Cantero et al., 1997). Our material was collected off Deception Island, in the South Shetland Islands.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFF8BA7733A4602D8FE0773C4.taxon	description	(figure 10) Oswaldella herwigi El Beshbeeshy, 1991: 259 – 265, figure 66; Peña Cantero et al., 1997: 344; Peña Cantero and García Carrascosa, 1998: 179; 1999: 214; Peña Cantero and Vervoort, 1998: 36; Peña Cantero and Marques, 1999: 85. Material examined. 11 / 958, numerous stems up to 24 mm high (USNM 1003330; RMNH-Coel. 30215; MNCN 2.03 / 235); 6 / 339, two stem fragments up to 20 mm long (USNM 1003331); 6 / 340, several stems a few millimetres high (USNM 1003332); 6 / 342, two incipient stems (USNM 1003333). Description. Stem monosiphonic, either branched or unbranched. Hydrocauli provided with alternately arranged apophyses, forming two longitudinal series, sometimes arranged in two planes meeting at an obtuse angle (up to 90 °) (figure 10 B, C). Apophyses directed upwards at an angle of ca 45 ° with long axis of stem. Each apophysis provided with an axillary nematophore emerging through a simple perisarc hole and a second nematophore emerging through a ‘ mamelon’ situated on one side of the apophysis (figure 10 B – D). Stem divided into internodes with one apophysis each. Cauline apophyses supporting hydrocladia separated by a distinct node (figure 10 B, C). Second-order hydrocladia present (figure 10 A); in one stem with incipient third-order hydrocladia. Hydrocladial arrangement asymmetrical (figure 10 A); first-order hydrocladia giving rise to several secondary hydrocladia. Top of distal hydrocladial internodes truncated. Hydrocladia heteromerously segmented (figure 10), with alternately arranged athecate and hydrothecate internodes. Hydrothecate internodes with one hydrotheca and two nematophores (figure 10 E – G): one mesial inferior emerging through a perisarc hole on a slight elevation of internode and provided with a scale-shaped nematotheca, and a mesial superior nematophore emerging through a perisarc hole situated behind the free adcauline hydrothecal wall. Hydrothecae usually situated on distal half of hydrothecate internodes; sometimes in the middle (figure 10 A, C, E, G). Hydrotheca shallow, rim circular and slightly laterally depressed, tilted downwards. Considerable part of adcauline wall of hydrotheca free; abcauline wall at an angle of ca 60 ° with internodal long axis. Gonothecae absent. Remarks. Oswaldella herwigi is the only species of the genus found outside Antarctic waters (cf. figure 19). It also has peculiarities in which it differs from the remaining species of Oswaldella. For example, the ‘ mamelon’ present on the cauline apophyses of this species has a structure different from that of the other species, as it is provided with a conical distal structure (figure 10 D) that is absent in the remaining species. Moreover, the naked nematophores, i. e. the mesial superior nematophore situated behind free adcauline hydrothecal wall and the axillary nematophore of the cauline apophyses appear to be sheathed (figure 10 C, E – G). Oswaldella herwigi is also the only species with heteromerously divided hydrocladia, having alternating hydrothecate and athecate internodes. In two stems from Stn 6 / 340 the cauline apophysis of the first stem internode has two axillary perisarc holes. In the second internode, those axillary holes are partly merged. In the remaining cauline apophyses there is a single axillary perisarc hole. This phenomenon is similar to that observed in other species of the genus (e. g. O. bifurca) and points to a certain inconsistency in the number of axillary nematophores. Ecology and distribution. Oswaldella herwigi is endemic to the Patagonian region (El Beshbeeshy, 1991), having been collected at depths from 90 to 1000 m on the Patagonian shelf and slope (El Beshbeeshy, 1991). Our material comes from depths of 44 to 586 m off the Falkland Islands and the western mouth of the Strait of Magellan. We found it growing as an epibiont on hydroids (Nemertesia sp. and Aglaopheniidae).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFB5A77139D10001FB2A73B6.taxon	description	(figure 11)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFB5A77139D10001FB2A73B6.taxon	materials_examined	Material examined. 691 / 023, one stem ca 35 mm high, with a single hydrocladium (USNM 1003334); 691 / 27, two stems and one stem fragment up to 80 mm high, with male gonothecae (USNM 1003335; RMNH-Coel. 30216; MNCN 2.03 / 236); 7 / 484, two stems up to 60 mm high (USNM 1003336); 721 / 776, one basally broken stem ca 60 mm high, with male gonothecae (USNM 1003337); 721 / 801, one stem ca 48 mm high (USNM 1003338). Description. Colonies composed of monosiphonic and unbranched stems (forked in the material from Stn 7 / 484), provided with apophyses alternately arranged in one plane and forming two longitudinal series. Apophyses directed upwards at an angle of ca 45 °. Stem divided into internodes with one apophysis each. Cauline apophyses supporting hydrocladia; up to second-order hydrocladia present (figure 11 A). Node separating cauline apophyses and hydrocladia inconspicuous (figure 11 B). Cauline apophyses provided with two axillary nematophores, each emerging through an axillary perisarc hole (figure 11 B); ‘ mamelons’ absent. Top of distal hydrocladial internodes truncated. Hydrocladia homomerously segmented; internodes each with one hydrotheca and two nematophores (figure 11 C – G): one mesial inferior emerging through a perisarc hole on a slight elevation of the internode and provided with a scale-shaped nematotheca, and one mesial superior emerging through a perisarc hole situated behind the free adcauline hydrothecal wall. Hydrothecae placed either in middle of hydrocladial internode or on its distal half (figure 11 A, C – G). Hydrotheca elongate, with circular aperture slightly tilted adcaudally. Rim even; sometimes with a tiny adcauline elevation. Abcauline wall of hydrotheca slightly convex, or straight; angle with long axis of internode 30 ° or less. Free adcauline hydrothecal wall distinct. Male gonothecae present, inserted at hydrothecal base on elevation of internode (figure 11 A), fusiform, with a subterminal, oval aperture (figure 11 A, H). Remarks. Oswaldella incognita is a well-characterized species, easily recognizable by the unbranched stems divided into internodes, the presence of secondary hydrocladia only, the existence of two axillary nematophores on the cauline apophyses and the shape of the hydrotheca (cf. table 1). Ecology and distribution. Oswaldella incognita has been found at depths from 234 (Peña Cantero and García Carrascosa, 1995) to 414 m (Peña Cantero et al., 1997); our material comes from 73 to 952 m. Peña Cantero and García Carrascosa (1995) found fertile colonies in January; colonies with gonothecae in our material were collected in January and February. The species was previously known only from off Elephant Island (Peña Cantero and García Carrascosa, 1995; Peña Cantero et al., 1997). Our material comes from north of the South Orkney Islands, off Brabant Island (Palmer Archipelago), off Deception and Livingston Islands (South Shetland Islands) and off Low Island.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFB7A7743A0903F3FD8675B4.taxon	description	(figure 12; table 3) Material examined. 12 / 1003, four stem fragments up to 20 mm long (holotype, USNM 1003339; paratypes, RMNH-Coel. 30217 and MNCN 2.03 / 237); 32 / 2018, one distally broken stem ca 9 mm high (USNM 1003340); 32 / 2021, two stem fragments up to 7 mm long, each with a single hydrocladium (USNM 1003341). Hydrothecae Length of abcauline wall 120 – 200 Length of free part of adcauline wall 30 – 50 Diameter at rim 180 – 230 Nematothecae Length 20 – 30 Internode Length 750 – 1150 Diameter under hydrotheca 180 – 230 Description. Colonies apparently with monosiphonic and unbranched stems, but present material fragmentary, largest fragment up to 20 mm long. Hydrocaulus with apophyses alternately arranged in one plane, forming two longitudinal series (figure 12 A). Cauline apophyses directed upwards, at an angle of ca 45 ° with long axis of stem and provided with three (figure 12 B, C) or four (figure 12 D) nematophores: two axillary nematophores, each emerging through a simple perisarc hole, and one or two nematophores emerging through a strongly developed ‘ mamelon’, situated laterally on upper part of apophysis. Hydrocaulus divided into internodes with one or two apophyses per internode (figure 12 A). Cauline apophyses supporting hydrocladia (figure 12 A – D) from which they are separated by distinct node; secondary hydrocladia present (figure 12 B). Hydrocladia homomerously segmented; hydrothecate internodes with one hydrotheca and two nematophores (figure 12 C – K): one mesial superior emerging through a simple perisarc hole just behind free adcauline hydrothecal wall and another mesial inferior nematophore, emerging through a perisarc hole on a strong elevation of the internode and provided with a small, scale-shaped nematotheca. Top of distal hydrocladial internodes truncated. Hydrotheca shallow, situated in middle of hydrocladial internode or on its distal half (figure 12). Hydrothecal aperture circular and distinctly tilted downwards. Adcauline wall of hydrotheca with considerable free part. Abcauline wall straight, angle with long axis of internode ca 45 °. Gonothecae absent. Remarks. Oswaldella medeae sp. nov. is well characterized by the shape of the hydrotheca, with a strong downward tilt, and by the presence of one or two ‘ mamelons’ on the cauline apophyses, besides two axillary nematophores (cf. table 1). Oswaldella medeae sp. nov. is allied to O. grandis by the presence of two axillary nematophores and two ‘ mamelons’, as well as by the general shape of the hydrotheca which is also shallow (cf. table 1). They are clearly different as in O. grandis the hydrotheca is almost fully adnate to the hydrocladial internode, the abcauline wall is very steep and the hydrothecal aperture is perpendicular to the long axis of the internode. They also differ in the general structure of the colony, since O. grandis is a much more robust species, with stems reaching 500 mm height. On the other hand, the cauline apophyses are relatively shorter and in close contact with the stem. Also, the hydrocladia are much more branched, having several third-order hydrocladia. Finally, in O. grandis the mesial inferior nematotheca is much more reduced. By the occasional presence of one ‘ mamelon’ besides the two axillary nematophores O. medeae sp. nov. is allied to O. antarctica, O. crassa, O. garciacarrascosai, O. obscura and O. vervoorti (cf. table 1). However, O. medeae sp. nov. clearly differs from those species. Oswaldella antarctica, O. crassa, O. garciacarrascosai and O. obscura have elongate hydrothecae, whereas in O. medeae sp. nov. these are shallow. In this character O. medeae sp. nov. is also close to O. vervoorti, though in this species the hydrotheca is larger and always situated on the distal half of internode, the hydrothecal aperture is approximately perpendicular to the long axis of the internode, and the mesial inferior nematotheca is larger. In O. vervoorti hydrocladia up to fourth-order are present, whereas in O. medeae sp. nov. only secondary hydrocladia have been observed. The presence of a shallow hydrotheca with a strong downward tilt of the rim brings O. medeae sp. nov. near to O. herwigi (cf. table 1), but in this species, together with one ‘ mamelon’, there is a single axillary nematophore on the cauline apophyses. Moreover, the asymmetrical structure of the hydrocladia is completely different and hydroids of that species have alternately arranged hydrothecate and athecate internodes. Oswaldella encarnae also has hydrothecae in which the rim is slightly tilted downwards (cf. table 1), but in this species the hydrothecae are distinctly larger, the hydrocladia are unbranched and there are only axillary nematophores on the cauline apophyses, with ‘ mamelons’ being absent. Ecology and distribution. Oswaldella medeae sp. nov. appears to have a circum- Antarctic distribution. It was collected at depths between 210 and 503 m at Pennell Bank (Victoria Land), in the Ross Sea region, and at the north-east of Joinville Island (Antarctic Peninsula). Etymology. The specific name medeae is a dedication to Medea Peña Sancho, daughter of the first author.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFB2A77A3A3605F0FCAB70CD.taxon	description	(figure 13; table 4) Material examined. 12 / 1002, one stem fragment ca 15 mm long (holotype, USNM 1003342). Description. Colonies composed apparently of monosiphonic and unbranched stems (figure 13 A). Hydrocaulus provided with apophyses alternately arranged in one plane, forming two longitudinal rows. Cauline apophyses directed upwards, forming an angle of ca 45 ° with long axis of stem and provided with two nematophores (figure 13 B – D): one axillary emerging through a simple perisarc hole and another emerging through a ‘ mamelon’, placed laterally on upper surface of apophysis. Stem divided into internodes; one apophysis per internode. Cauline apophyses supporting hydrocladia (figure 13 A – C); up to secondary hydrocladia present. A distinct node separates cauline apophysis and hydrocladium. Hydrocladia homomerously divided into internodes each provided with one hydrotheca and two nematophores (figure 13 E, F): one mesial superior emerging through a simple perisarc hole situated just behind free adcauline hydrothecal wall, and one mesial inferior emerging through a hole situated on a sharp elevation of the internode and provided with a much-reduced nematotheca. Top of distal hydrocladial internodes truncated. Hydrotheca elongate, placed nearly in the middle of internode (figure 13 E, F). Hydrothecal aperture circular, rim even and more or less perpendicular to long axis of internode. Adcauline hydrothecal wall with a distinct free part. Abcauline wall approximately straight, but sometimes convex basally and with a slight distal concavity. Gonothecae absent. Remarks. In spite of the scarcity of material, O. monomammillata sp. nov. is a well-characterized species, clearly distinguishable from the remaining species of the genus (cf. table 1). Hydrothecae Length of abcauline wall 200 – 300 Length of free part of adcauline wall ca 30 Diameter at rim 170 – 200 Nematothecae Length ca 20 Internode Length 740 – 930 Diameter under hydrotheca 150 – 175 Oswaldella monomammillata sp. nov. is allied to O. garciacarrascosai in general aspect of the colony and in shape of the hydrothecae (cf. table 1). Differences concern the number of nematophores on the cauline apophyses, since in O. garciacarrascosai there are two axillary nematophores and one ‘ mamelon’, whereas in O. monomammillata sp. nov. there is a single axillary nematophore besides the ‘ mamelon’. They also differ because in O. garciacarrascosai there is no nematotheca at the mesial inferior nematophore of the hydrocladial internodes, whereas in O. monomammillata sp. nov. there is a much-reduced nematotheca. The hydrothecae in O. garciacarrascosai are also slightly larger; Peña Cantero et al. (1997) reported a length of the abcauline hydrothecal wall of 228 – 312 M m, whereas in O. monomammillata sp. nov. that length is 240 – 280 M m. In the shape of the hydrotheca O. monomammillata sp. nov. also resembles O. delicata, but these species differ in the number of nematophores present on the cauline apophyses (cf. table 1); in O. delicata there is a single axillary nematophore emerging through a perisarc hole, whereas in O. monomammillata sp. nov. there is also a ‘ mamelon’. They also differ in the development of the mesial inferior nematotheca, since in O. delicata there is a conspicuous scale-shaped nematotheca, whereas in O. monomammillata sp. nov. that nematotheca is much less developed, being rather inconspicuous. Moreover, in O. monomammillata sp. nov. the hydrocladia are bifurcated but in O. delicata usually unbranched. Ecology and distribution. Oswaldella monomammillata sp. nov. was collected at 265 m depth off Elephant Island. Etymology. The specific name monomammillata refers to the presence of a single ‘ mamelon’ at the cauline apophysis.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFB2A77A3A3605F0FCAB70CD.taxon	discussion	Remarks. Oswaldella obscura is characterized by the polysiphonic and branched stems, the presence of mesial inferior nematothecae in the hydrocladial internodes, the presence of two axillary nematophores and one ‘ mamelon’ in the cauline apophyses and the presence of only secondary hydrocladia (cf. table 1). Ecology and distribution. Oswaldella obscura has been found on muddy bottoms at depths between 260 and 830 m, along the south and east coasts of the Weddell Sea. Fertile colonies were found in January and February. It is used as a substratum by other hydroids (Peña Cantero et al., 1997).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFBDA77B39C706B5FE4374B7.taxon	discussion	Remarks. Oswaldella rigida is well characterized by the branched stems, the angle of 70 – 90 ° formed between the cauline apophyses and the stem, the absence of a node between the cauline apophyses and the hydrocladia, the shape of the hydrotheca, provided with an adcauline elevation, and the presence of two axillary nematophores on the cauline apophyses (cf. table 1). Ecology and distribution. Oswaldella rigida is a shelf species, having been found at depths from 80 to 830 m on muddy and rocky bottoms (Peña Cantero et al., 1997). Oswaldella rigida appears to have a circum-Antarctic distribution (Peña Cantero et al., 1997). It is known from the Davis Sea (Vanhöffen, 1910) in East Antarctica, and at the east coast of the Weddell Sea (Peña Cantero et al., 1997) in West Antarctica.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFBDA7793A5A04E7FE157011.taxon	description	(figure 14)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFBDA7793A5A04E7FE157011.taxon	materials_examined	Material examined. 6 / 445, one stem ca 11 mm high (USNM 1003343); 691 / 023, one stem ca 45 mm high in bad condition (USNM 1003344); 691 / 23, numerous broken stems without hydrocladia; only one stem ca 45 mm high with hydrocladia and with a single gonotheca (USNM 1003345); 691 / 24, two stems up to 40 mm high (USNM 1003346); 691 / 27, several stems up to 90 mm high, with gonothecae (USNM 1003347; RMNH-Coel. 30218; MNCN 2.03 / 238); 7 / 484, one stem ca 42 mm high (USNM 1003348); 721 / 1063, two stem fragments up to 28 mm long, with gonothecae (USNM 1003349; RMNH-Coel. 30219); 721 / 704, one colony with several stems up to 170 mm high (USNM 1003350; RMNH-Coel. 30220; MNCN 2.03 / 239); 721 / 801, one distal stem fragment ca 30 mm long (USNM 1003351); 721 / 816, numerous stems up to 170 mm high, with gonothecae (USNM 1003352; RMNH-Coel. 30221; MNCN 2.03 / 240); 731 / 1944, three stems up to 25 mm high (USNM 1003353); 824 / 013 - 1, three fragments or stems up to 50 mm high (USNM 1003354); 824 / 030 - 1, eight stems up to 85 mm high, with gonothecae (USNM 1003355; RMNH-Coel. 30222); 824 / 040 - 1, one stem fragment ca 4 mm long, with a single gonotheca (USNM 1003356); 833 / 022 - 4, numerous stems up to 110 mm high, with male gonothecae (USNM 1003357; RMNH-Coel. 30223; MNCN 2.03 / 241); SOSC-L 46, one distally truncated stem ca 18 mm high, with gonothecae (USNM 1003358). Description. Stems polysiphonic and unbranched, divided into internodes. Sometimes colonies apparently with branched stems, but actually such ‘ secondary’ stems originate from stolons ascending on ‘ main’ stems. Hydrocaulus provided with alternately arranged cauline apophyses, forming two longitudinal series; usually one or two, sometimes three, apophyses per internode. Cauline apophyses forming an angle of ca 45 ° with long axis of cauline internodes, provided with four nematophores (figure 14 B): two emerging through axillary perisarc holes and two additional nematophores each emerging through a ‘ mamelon’; occasionally a single ‘ mamelon’ present. Cauline apophyses supporting much-branched hydrocladia (figure 14 A); up to fourth-order hydrocladia observed, hydrocladial arrangement symmetrical. No node between cauline apophysis and hydrocladium (figure 14 A, B). Top of distal hydrocladial internodes pointed; occasionally truncated. Hydrocladia homomerously segmented, all internodes hydrothecate and provided with one hydrotheca and two nematophores (figure 14 C – F): one mesial inferior emerging through a simple perisarc hole situated at dorsal surface of strong elevation of internode (without remnants of nematothecae) and one mesial superior nematophore, emerging through a perisarc hole situated behind free adcauline hydrothecal wall. Hydrotheca placed in middle of hydrocladial internode (figure 14 C – F), elongate, part of adcauline wall free. Abcauline wall slightly convex; aperture kidney-shaped, slightly tilted adcaudally and strongly depressed at adcauline side. Male and female gonothecae present, inserting on hydrocladial internodes directly under inferior nematophore. Both male and female gonothecae pear-shaped; gonothecal aperture circular, large and situated at distal oblique end. Female gonothecae (figure 14 G) much larger than male ones (figure 14 H). Remarks. This is a common and well-characterized Antarctic species (cf. table 1). It is easily recognizable by the strong division of the stems into internodes, the abundant branching of the hydrocladia, the presence of two axillary nematophores and two ‘ mamelons’ on the cauline apophyses, the absence of a mesial inferior nematotheca at the hydrocladial internodes and the shape of hydrothecae and gonothecae. Ecology and distribution. Oswaldella shetlandica is a shelf species (Peña Cantero et al., 1995), having been recorded at depths from 30 (Stepan’yants, 1979) to 216 m (Peña Cantero et al., 1995); our material comes from 44 to 952 m. It has been found on rocky (Stepan’yants, 1979) and stony bottoms (Peña Cantero et al., 1995). We have found it epibiotic on hydroids (Billardia subrufa and Staurotheca sp.). Oswaldella shetlandica has been collected with gonothecae in January and February (Peña Cantero et al., 1995). In our material, fertile colonies were collected in January, February, March, April and December. Oswaldella shetlandica appears to be endemic to West Antarctica, where it has been reported from off King George Island, in the South Shetland Islands (Stepan’yants, 1979; Peña Cantero et al., 1995) and off Low Island (Blanco and De Redolatti, 1977). Our material comes from off King George, Livingston and Nelson Islands (South Shetland Islands), Anvers and Brabant Islands (Palmer Archipelago), Low Island, Argentine Island (Antarctic Peninsula) and from north of the South Orkney Islands.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFBFA77C3A600054FD5474CE.taxon	description	(figure 15)	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFBFA77C3A600054FD5474CE.taxon	materials_examined	Material examined. 000 AG, one stem at least 210 mm high (USNM 1003359); 000 AH, one fragmented stem, at least 220 mm high, with gonothecae (USNM 1003360; RMNH-Coel. 30224); 00 DAF, several stems of at least 300 mm high (USNM 1003361; RMNH-Coel. 30225); 00 DAQ, four stems up to 320 mm high (USNM 1003362); 12 / 1003 several fragments up to 32 mm long (USNM 1003363); 27 / 1896, numerous stem fragments up to 100 mm long, with immature gonothecae (USNM 1003364; RMNH-Coel. 30226; MNCN 2.03 / 242); 32 / 2080, one fragmented stem (largest fragment ca 120 mm long) (USNM 1003365; RMNH-Coel. 30227); 32 / 2082; three stem fragments up to 50 mm long (USNM 1003366); 32 / 2121, numerous stem fragments up to 70 mm long, with gonothecae (USNM 1003367); 32 / 2125, one fragmented stem (largest fragment up to 90 mm long), with gonothecae (USNM 1003368; RMNH-Coel. 30228; MNCN 2.03 / 243); 6 / 418, several fragments up to 50 mm long, with gonothecae (USNM 1003369); 691 / 26, numerous fragments up to 220 mm long (USNM 1003370; RMNH-Coel. 30229; MNCN 2.03 / 244); 767, two stem fragments up to 60 mm long (USNM 1003371); 833 / 018 - 1, one stem ca 500 mm high (USNM 1003372; RMNH-Coel. 30230; MNCN 2.03 / 245). Description. Colonies consisting of polysiphonic and branched stems. Hydrocauli provided with apophyses alternately arranged in two longitudinal series, directed upwards, forming an angle of ca 45 ° with long axis of stem. Hydrocaulus divided into internodes with one apophysis each; nodes, situated just above apophyses, often incomplete, as a result many internodes apparently with two apophyses. Cauline apophyses typically provided with two dorsal nematophores (figure 15 B), each one emerging through a ‘ mamelon’ which may occasionally be absent (for instance in the material from Stn 6 / 418), and from two to six axillary nematophores (figure 15 B) emerging through simple perisarc holes. Cauline apophyses supporting hydrocladia (figure 15 A) from which they are separated by a distinct node, usually followed by a series of short, athecate internodes. Up to fourth-order hydrocladia present; hydrocladial arrangement symmetrical (figure 15 A). Hydrocladia homomerously segmented; all internodes hydrothecate with one hydrotheca in middle of internode and two nematophores (figure 15 C – H): one mesial inferior emerging through a perisarc hole on slight elevation of internode and provided with a scale-shaped nematotheca, and another mesial superior nematophore emerging through a perisarc hole behind free portion of adcauline hydrothecal wall. Top of distal hydrocladial internodes truncated. Hydrotheca elongate (figure 15 C – H); rim circular and even, slightly tilted adcaudally. Adcauline wall of hydrotheca with distinct free portion; abcauline wall straight. Gonothecae present, inserting on infrathecal elevation of hydrocladial internodes, fusiform, with subterminal aperture (figure 15 I). Remarks. Oswaldella stepanjantsae is well characterized by the general appearance of the colony, by the presence of two ‘ mamelons’ and two to six axillary nematophores on the cauline apophyses (cf. table 1), and by the shape of hydrothecae and gonothecae. Ecology and distribution. Oswaldella stepanjantsae has been found at depths between 50 and 600 m (Broch, 1948); our material comes from 36 to 1890 m. It occurred on muddy, sandy and stony bottoms and on bottoms composed of mud and sand or small stones (Broch, 1948). It has been found with gonothecae in January and February (Peña Cantero et al., 1997); our fertile material was collected in January, February and December. It is used as a substratum by other hydroids: Peña Cantero et al. (1997) found colonies of Hydractinia sp., Halecium sp. and we have observed colonies of Abietinella sp., Billardia subrufa, Campanularia sp., Filellum sp., Hydractinia sp., Sertularella sp. and Symplectoscyphus sp.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFBAA77C39A60508FD21728F.taxon	discussion	Remarks. Oswaldella terranovae is characterized by the branched stems, the presence of a much reduced mesial inferior nematotheca in the hydrocladial internodes, the shape of the hydrotheca, and the presence of two axillary nematophores and two ‘ mamelons’ on the cauline apophyses (cf. table 1). Ecology and distribution. Oswaldella terranovae is known only from off Cape Adare, Ross Sea, where it was found at depths of 82 – 92 m, on a bottom of pebbles (Peña Cantero and Vervoort, 1996).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFBAA762399902C6FD147769.taxon	discussion	Remarks. Oswaldella tottoni is well characterized by the shape of the hydrotheca, which is low and situated on the distal half of the hydrocladial internodes, the presence of two axillary nematophores on the cauline apophyses, and the presence of only secondary hydrocladia (cf. table 1). Ecology and distribution. Oswaldella tottoni is a shelf species (Peña Cantero et al., 1997), having been found at depths from 256 (Peña Cantero and Vervoort, 1996) to 400 m (Peña Cantero et al., 1997) on muddy bottoms. Oswaldella tottoni seems to have a circum-Antarctic distribution. It is known from McMurdo Sound, Ross Sea (Peña Cantero and Vervoort, 1996), in East Antarctica, and from the east coast of the Weddell Sea (Peña Cantero et al., 1997), in West Antarctica.	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFBAA762399902C6FD147769.taxon	materials_examined	Material examined. 6 / 415, one stem ca 11 mm high (USNM 1003373); 6 / 445, four stem fragments up to 33 mm long (USNM 1003374); 691 / 002 - B, numerous fragments and stems up to 20 mm high (USNM 1003375; RMNH-Coel. 30231; MNCN 2.03 / 246); 691 / 023, two stem fragments up to 25 mm high, with one immature gonotheca (USNM 1003376); 691 / 24, five stem fragments up to 45 mm long (USNM 1003377); 7 / 484, two stem fragments up to 35 mm long (USNM 1003378); 721 / 1062, one stem ca 46 mm high (USNM 1003379); 721 / 1063, three stems up to 28 mm high (USNM 1003380; RMNH-Coel. 30232); 721 / 704, four stems up to 30 mm high (USNM 1003381; RMNH-Coel. 30233); 721 / 816, one stem ca 40 mm high (USNM 1003382); SOSC-L 42, one stem ca 33 mm high, with immature gonothecae (USNM 1003383). Description. Colonies composed of monosiphonic and unbranched stems up to 45 mm high. Stems with alternately arranged apophyses forming two longitudinal rows, directed upwards and forming an angle of ca 45 ° with long axis of hydrocaulus. Stems divided into internodes with one, occasionally two apophyses per internode, each provided with three nematophores (figure 16 B): two axillary nematophores, each emerging from a simple perisarc hole, and another emerging through a ‘ mamelon’ and occasionally absent. Cauline apophyses supporting hydrocladia from which they are separated by distinct node (figure 16 B); up to third-order hydrocladia observed (figure 16 A). Hydrocladia homomerously divided into hydrothecate internodes with one hydrotheca and two nematophores (figure 16 C – H): one mesial superior nematophore emerging from a perisarc hole situated behind free adcauline hydrothecal wall and one mesial inferior nematophore with a scale-shaped nematotheca and emerging through a perisarc hole situated on slight elevation of internode. Top of distal hydrocladial internodes truncated. Hydrotheca shallow, situated on distal half of hydrocladial internode (figure 16 C – H). Hydrothecal aperture perpendicular to long axis of internode, sometimes slightly tilted adcaudally; rim circular and even. Adcauline wall of hydrotheca with distinct free portion; abcauline wall straight, angle with internodal long axis ca 30 °. Immature gonothecae present, inserting on elevation of hydrocladial internode just under mesial inferior nematotheca. Gonotheca cone-shaped; maximum diameter at distal, truncated part (figure 16 I). Remarks. Oswaldella vervoorti is an easily recognizable species (cf. table 1), being characterized by the shape of the hydrotheca, the position of the hydrotheca on the distal half of the hydrocladial internodes, the much-branched hydrocladia and the presence of two axillary nematophores and one ‘ mamelon’ on the cauline apophyses. Ecology and distribution. Oswaldella vervoorti was previously known only from off Livingston Island, in the South Shetland Islands, where it was found at a depth of 46 m on muddy bottoms, epibiotic on ascidians (Peña Cantero and García Carrascosa, 1998). Our material comes from depths of 44 to 952 m. Immature gonothecae were found in February. We found it epibiotic on hydroids (Schizotricha sp.). Oswaldella vervoorti appears to be endemic in West Antarctica. It had been reported from off Livingston Island, in the South Shetland Islands (Peña Cantero and García Carrascosa, 1998). Our material was collected north of the South Orkney Islands, north of d’Urville Island (Antarctic Peninsula), north-east of Livingston Island and off Nelson and King George Islands (South Shetland Islands) and off Brabant Island (Palmer Archipelago).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFA4A7613AC90794FD3F7769.taxon	description	(figure 17) Material examined. 6 / 416, one stem broken into two fragments (35 and 20 mm long) (USNM 1003384); 6 / 426, a few stems up to 70 mm high (USNM 1003385; RMNH-Coel. 30234); 6 / 428, one stem ca 18 mm high (USNM 1003386); 6 / 445, two fragments of one stem (USNM 1003387); 691 / 023, three basally broken stems up to 25 mm high (USNM 1003388; RMNH-Coel. 30235); 691 / 24, two stems up to 15 mm high (USNM 1003389). Description. Colonies composed of monosiphonic and unbranched stems up to 70 mm high. Hydrocaulus with apophyses alternately arranged in one plane, forming two longitudinal rows and directed upwards, forming an angle of ca 45 ° with long axis of stem (figure 17 A). Cauline apophyses provided with two axillary nematophores, each one emerging from a simple perisarc hole (figure 17 B). Hydrocaulus divided into internodes (figure 17 A); one to three apophyses per internode, each apophysis supporting an unbranched hydrocladium (figure 17 A), though secondary hydrocladia are also present (figure 17 B). A distinct node separating cauline apophyses and hydrocladia (figure 17 A, B). Hydrocladia homomerously divided into internodes, each with one hydrotheca and two nematophores (figure 17 C – K): one mesial superior, emerging from a simple perisarc hole behind free adcauline hydrothecal wall, and one mesial inferior nematophore with a much-reduced, scale-shaped nematotheca emerging from a perisarc hole in an elevation of the internode. Top of distal hydrocladial internodes truncated. Hydrotheca elongate, situated approximately in the middle of hydrocladial internode (figure 17 C – K), provided with a long free part of its adcauline wall (up to half of its length). Abcauline hydrothecal wall straight, though slightly convex basally; sometimes with a slight concavity at distal end. Hydrothecal aperture with circular and even rim, approximately perpendicular to long axis of internode. Gonothecae absent. Remarks. Oswaldella sp. 1 is allied to O. delicata (cf. table 1), sharing with it the general appearance and structure of the colony. These two differ in the number of axillary nematophores; in O. delicata there is a single axillary nematophore, in Oswaldella sp. 1 there are two, each one emerging from a perisarc hole. They also differ in greater length of the free adcauline hydrothecal wall in Oswaldella sp. 1. Additional fertile material is necessary to define the systematic status of the present material. Ecology and distribution. Oswaldella sp. 1 was found at depths from 93 to 507 m near the Antarctic Peninsula: off Brabant Island (Palmer Archipelago), north-east of Livingston Island (South Shetland Islands) and north of d’Urville Island and Penguin Island (Bransfield Strait).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
038687FCFFA7A7613AC9079AFC127047.taxon	description	(figure 18) Material examined. 000 AZ, one stem ca 47 mm high, almost without hydrocladia (USNM 1003390); 000 DW, six stem fragments up to 100 mm long (USNM 1003391; RMNH-Coel. 30236). Description. Stems unbranched and apparently monosiphonic. Stem provided with apophyses alternately arranged in one plane, forming two longitudinal series. Cauline apophyses directed upwards, forming an angle of ca 45 ° with longitudinal axis of stem and provided with two axillary nematophores (figure 18 B), each one emerging from a simple perisarc hole. Stem divided into internodes, each with one apophysis supporting hydrocladia that are usually bifurcated and have two secondary hydrocladia (figure 18 A); third-order hydrocladia are also present. Hydrocladial arrangement symmetrical (figure 18 A). A distinct node separating cauline apophyses and hydrocladia (figure 18 A, B). Hydrocladia homomerously divided into hydrothecate internodes with one hydrotheca and two nematophores (figure 18 C – G): one mesial superior emerging from a perisarc hole behind free adcauline hydrothecal wall, and one mesial inferior nematophore provided with a scale-shaped nematotheca, emerging from a perisarc hole in a slight elevation of internode. Top of distal hydrocladial internodes truncated. Hydrotheca elongate, placed on distal half of internode (figure 18 C – G). Hydrothecal aperture slightly tilted adcaudally, rim circular and even. Adcauline wall with a distinct free portion; abcauline wall almost straight, angle with long axis of internode very acute. Gonothecae absent. Remarks. Oswaldella sp. 2 is allied to O. incognita (cf. table 1), sharing the division of the stem into internodes, the presence of two axillary nematophores on the cauline apophyses and the general shape of the hydrothecae. There are, nevertheless, distinct differences, such as the longer hydrocladial internodes and shorter hydrothecae in Oswaldella sp. 2. Also, in Oswaldella sp. 2 the hydrothecae are placed on the distal half of the internodes, whereas in O. incognita they occur approximately in the middle. Finally, in O. incognita only secondary hydrocladia have been reported whereas in Oswaldella sp. 2 third-order hydrocladia have also been observed. These differences, along with the absence of gonothecae in the present material, prevent us from properly evaluating the systematic position of Oswaldella sp. 2. Ecology and distribution. Oswaldella sp. 2 was found at depths from 18 to 146 m, north of Wilkes Station, at the Budd Coast (Wilkes Land).	en	Peña Cantero, A. L., Vervoort, W. (2004): Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species. Journal of Natural History 38: 805-861
