taxonID	type	description	language	source
0393CF4AD721FFFCFF22BB3FFE29FCB5.taxon	materials_examined	Type: — GUAM. Outhouse Beach, Apra Harbor, 13.464 N, 144.656 E, in a collection of microalgal coating on calcareous sand, ca. 15 m depth. C. S. Lobban and M. Schefter, 13 Dec. 2010. Holotype CAS! frustule located 17.0 mm E and 7.4 mm S of the mark on slide 1696, from sample GU 52 O- 4, slide 1696, accession # 627432, slide # 223050, shown in Figures 1 and 2.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD721FFFCFF22BB3FFE29FCB5.taxon	etymology	Etymology: — With reference to the marginal longitudinal striae.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD721FFFCFF22BB3FFE29FCB5.taxon	description	Description: — The sigmoid frustules were broad in the middle in both valve and girdle view, narrowing and then expanding into spathulate apices both deflected in the same direction (Figs 1, 2), achieved by the twisting of the frustule through one of the narrow parts (Fig. 3), characteristic of the genus. Valves had very little mantle. Areolae in transapical and longitudinal striae (Figs 1 – 5); the longitudinal striae were deflected slightly around the central area and there were two marginal rows parallel to the valve margin (Fig. 4). On the side to which the apices curved, the longitudinal striae were exactly parallel to the raphe, but on the opposite side they curved slightly relative to the raphe (Fig. 4). External openings of the areolae were slits, but their orientation varied across the valve face (Figs 4, 5). In the two rows closest to the sternum, almost all slits were oriented apically; in rare cases where two areolae were joined by a continuous slit, the areolae were adjacent in the apical direction (Fig. 4, arrowheads). There were no V-shaped slits joining areolae transapically in these striae, in contrast to A. arenicolum and A. belizense. In the subsequent longitudinal striae many of the slits were oriented diagonally across the areolae (Fig. 5), although this was not consistent (compare Figs 4 and 5). In the two marginal longitudinal striae the outer row had consistently square areolae with generally apically oriented slits, whereas the second row areolae were often transapically elongated and had transapically elongated slits that sometimes joined the marginal areolar slit in an irregular V-shape (Fig. 5 arrows). A series of silica thickenings was evident between the longitudinal striae (Figs 4, 5), which were not present in A. arenicolum, suggesting that the surface of this species was slightly ridged, but we do not have images from an angle to confirm this. The axial area was very narrow and the raphe branches straight. There was a tiny elliptical central area (0.5 μm diam.), slightly displacing 4 – 5 transapical striae and making a wave in the longitudinal striae (Fig. 4). The external central raphe endings were simple and approximate. Terminal raphe endings were hooked (Fig. 6). Internal aspect was not observed in this species. Girdle bands appeared to be plain (Fig. 4); they were broad in the middle of the cell but became very narrow elsewhere.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD723FFFCFF22BE25FC3AF8D1.taxon	materials_examined	Type: — GUAM. Outhouse Beach, Apra Harbor, 13.464 N, 144.656 E, in a collection of microalgal coating calcareous sand, ca. 15 m depth. C. S. Lobban and M. Schefter, 13 Dec. 2010. Holotype CAS! frustule located 13.8 mm E and 7.3 mm S of the mark on slide 1696, from sample GU 52 O- 4, slide 1696, accession # 627432, slide # 223050, shown in Fig. 9.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD723FFFCFF22BE25FC3AF8D1.taxon	etymology	Etymology: — Latin, arenicola, - um, sand dwelling. Additional materials examined: — GU 52 V- 4	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD723FFFCFF22BE25FC3AF8D1.taxon	description	Description: — This species had sigmoid frustules with spathulate apices both deflected in the same direction (Figs 7, 9, 10). Frustules were nearly square in transapical section, because the copulae together were of similar width as the valve, and they tapered similarly toward the poles (Fig. 13). Thus frustules may lie in valve view, girdle view, or in between, and the appearance of the apices varied accordingly. In valve view the apices were very narrow; the spathulate expansion was apparent only when the apex was in girdle view (Figs 12, 13) and it was then compounded by the width of the copulae (Fig. 12); the striae across it had ca. 8 areolae. The frustule was twisted at one end, characteristic of the genus (Fig. 10). Two plate-like plastids lay along the valve faces, which may look ribbon-like in girdle view and there was a small plastid or extension at the apices (Figs 7, 8). Valve finely striated with very little mantle (Fig. 11, 13). Areolae formed transapical and longitudinal striae (Figs 11, 13, 14, 17); the external openings of the areolae were apically oriented slits, except for the frequent occurrence of transapically joined pairs of areolae in which the external opening was a V-shaped slit (Fig. 15). The axial area was very narrow and there was a tiny elliptical central area (4 μm diam.), that slightly displaced the longitudinal striae (Fig. 14). The external central raphe fissures are ended in small, overlapping pores (Fig. 14); the terminal fissures were hooked (Fig. 16). Internally, the raphe slit ran along the side of a rib (Fig. 17), the central nodule was flanked by central bars of silica (Fig. 17), and the termini ended in a helictoglossa (Fig. 18). The cingulum was plain, broad in the middle of the cell, becoming first very narrow and then broader toward the apices (Figs 12, 13). Arcuatasigma arenicolum was more common in the sample than A. marginale.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD724FFF9FF22BA0FFED4FB0E.taxon	materials_examined	Type: — BELIZE. Half Moon Bay, sublittoral sediment. RAF sub aqua team, 1979. Holotype BM-BP 168! Half Moon Bay, Belize # 24 (shown in figs 21, 26, 27); Paratype BM-BP 239! Half Moon Bay, Belize # 34 (shown figs 19, 23, 24); Paratype BM-BP 172! Half Moon Bay, Belize # 28 (shown in figs 20, 25, 27, 28).	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD724FFF9FF22BA0FFED4FB0E.taxon	etymology	Etymology: — With reference to the type locality.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD724FFF9FF22BA0FFED4FB0E.taxon	description	Description: — This species had a sigmoid frustule with one pole twisted 180 ° to give the arcuate appearance of the genus (Figs 19 – 21, 27). The valve had a shallow mantle. Areolae loculate (Fig. 28), arranged in longitudinal and transverse rows of striae (Figs 23 – 24). The spathulate apex was broad, with ca. 20 areolae in the striae. External areolae opened to apically elongate slits except in the occasional case of transapically joined pairs of areolae in which the external opening was V-shaped (Fig. 22); this also occurs in A. addu (Reid 2012, Plate 15, fig. 2). In one specimen the areolae appeared round, perhaps due to dissolution or being at an early stage of development so the openings have not been fully filled in (Cox & Kennaway 2004). Raphe eccentric, crossing the main body of the valve diagonally, becoming eccentric at the poles running close to the valve edge (Figs 19, 25). Terminal raphe fissure following the curvature of the edge of the pole, terminating on the valve mantle (Figs 25, 26). The external central raphe fissures completely overlapped (Fig. 22) as in A. addu and A. closterioides in contrast to the two Guam species, where there was no overlap or only the pores overlapped. Raphe sternum thickening was denser on the primary side of the valve. Internal central nodule (0.9 - 1 μm diam.) flanked either side by central bars (Fig. 24). Internally the raphe terminates in a helictoglossa at the pole (Fig. 23). Girdle bands were plain (Fig. 26). The appearance of the valve, as with other members of the genus varied greatly depending on the orientation it was lying (valve, girdle or somewhere in between Figs 19 – 21).	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD728FFF7FF22BBB9FDB6F833.taxon	materials_examined	Type locality: Balearic Islands, Mediterranean Sea.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD728FFF7FF22B891FE28F937.taxon	materials_examined	Type locality: Vairao Lagoon, Tahiti.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD729FFF6FF22BCF5FC99FDCF.taxon	materials_examined	Type (iconotype): Castracane 1886, pl. 26, fig. 15. Type locality: Port of Tahiti, French Polynesia. Synonym: Arcuatasigma challengeriensis (Castracane) G. Reid (2012: 90).	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD729FFF6FF22BFF1FF1CFB95.taxon	materials_examined	Type (iconotype designated here): Castracane 1886, pl. 26, fig. 14. Type locality: “ Tirreno Sea, ” in the Mediterranean (Tyrrhenian Sea), collected by Alessandro Garbi of Florence (vide Castracane). Etymology: Named for the collector. Synonym: Arcuatasigma castracanense G. Reid (2012) Diatom Monographs 14: pro parte, quoad pl. 13: fig. 5. There are now seven species of Arcuatasigma and two species of Toxonidisigma recognized, all of which are marine.	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
0393CF4AD729FFF6FF22BDC9FE23FEC3.taxon	diagnosis	Diagnosis. Sigmoid frustules with one apex twisted such that both apices curve in the same direction, striae decussate. Type species: Toxonisigma challengeriense (Castracane) Lobban & G. Reid Etymology: Gr., n., combining the name of Toxonidea (“ τόξο and ιδεα, bow-shaped ” — Donkin 1858, but properly τόξο + ιδιον, dimunitive bow) with σιγμα (the letter Σ).	en	Lobban, Christopher S., Reid, Geraldine (2018): New Arcuatasigma species (Bacillariophyta, Pleurosigmataceae) from Guam and Belize, and the taxonomic identities of Toxonidea challengeriensis and its variety. Phytotaxa 346 (2): 169-179, DOI: 10.11646/phytotaxa.346.2.4, URL: http://dx.doi.org/10.11646/phytotaxa.346.2.4
