Typhlosyrinx praecipua (E. A. Smith, 1899 )

Bouchet, P. & Sysoev, A., 2001, Typhlosyrinx - like tropical deep-water turriform gastropods (Mollusca, Gastropoda, Conoidea), Journal of Natural History 35 (11), pp. 1693-1715 : 1698-1699

Typhlosyrinx praecipua (E. A. Smith, 1899)

(figures 8–13)

Pleurotoma (Surcula) praecipua E.A. Smith, 1899: 239 .

Pleurotoma (Surcula) praecipua: Alcock and MacArdle, 1901 : pl. 9, figures 5, 5a.

Typhlosyrinx praecipua: Powell, 1969: 360 , pl. 272, figures 2, 3; Sysoev, 1996a: 23, figure 101.

Type material. Holotype ZSI M 915/1 (not seen, not available for loan), paratype BMNH 1904.615.53 .

Type locality. India, off Travancore coast, 09°29'34 " N, 75°38'E, 360 fms [658 m] [Investigator sta. 229].

Material examined. The paratype (figures 9, 10). Gulf of Aden . John Murray D eep-Sea Expedition: Sta. 184, 14°36'N, 51°00'E, 1270 m, one dd ( Sysoev, 1996: figure 101). Ceylon. Safari 2 : Sta. CP6, 08°11'N, 79°03'E, 1035 m, one lv (figures 12, 13). Sta. CP7 , 08°29'N, 79°19'E, 1095 m, two lv (figure 11) .

Distribution. Gulf of Aden, India, Ceylon, in 658–1270 m.

Description. Our description is based on the paratype (figures 9, 10), which differs rather substantially from the illustration of the holotype ( Alcock and MacArdle, 1901: pl. 9, figures 5, 5a; this paper, figure 8) in having a much more convex last whorl, more fl attened spire pro fi le, longer canal and low-set axial ribs. However, it is di ffi cult to estimate the value of these differences without actually examining the holotype. Holotype 38 ✕ 15 mm. The 33.0 ✕13.5 mm paratype has a white polished solid surface and a proportionally short spire occupying 29% of total shell height. Protoconch corroded but the ca 0.5 remaining whorl has a diagonally cancellated sculpture. Teleoconch whorls eight, with very broad and strongly convex last whorl, suture weakly channelled, sculptured by axial ribs except on ca last 1.7 smooth whorls, ribs very low-set on last two spire whorls, which makes suture wavy. Spiral striae rather distinct on fi rst four teleoconch whorls, obsolete on last spire whorls, very weak on last whorl below periphery, and slightly stronger on canal. Canal distinctly set off from shell base. Three specimens collected by the Safari 2 expedition (figures 11–13) have thin shells, with weakly shining surface. Whorls fl attened. Suture shallow, adpressed. Axial ribs short, strongly nodular, on last ribbed whorls restricted to area just above suture. Spiral sculpture very weak, consisting of closely set fl attened cords on periphery of ribbed whorls, indistinct cords on periphery and base of last whorls, and few stronger cords on canal. Colour brownish yellow, with broad, rather indistinct light-chestnut band above periphery.

Remarks. Typhlosyrinx praecipua as interpreted here is very similar to T. supracostata , differing only in the slightly lower spire and stronger and more nodulose axial ribs. Shells from the Safari 2 expedition are somewhat intermediate between the types of T. praecipua and our material of T. supracostata . This may indicate that the two nominal species represent only Indian and South-East Asian populations of a single taxonomical species. However, there is too little material available from the Indian Ocean to assess population variability there, and no material at all from between India and central Indonesia. Conservatively, we keep the two species as separate entities.