DEEP-SEA CONOIDEAN GASTROPODS 



29 



which disappear towards the body whorl, was mentioned by 

 Shepman for the much larger paratype. The prominent axial ribs 

 on the subsutural slope are seen in Thiele's figure of the species. 

 Judging from the published figures of B. trophonoidea, the 

 species is rather variable, though it can be mentioned that the 

 proportions of the shell (H/D and Hs/H) are rather constant in 

 different specimens. Thiele's figure illustrates a somewhat more 

 slender shell with better differentiated and more straight 

 siphonal canal and much longer axial ribs, almost reaching the 

 canal (they do not reach the whorl periphery in the holotype). 

 Okutani published an illustration of a shell with a high and 

 narrow spire. However, the variability of B. trophonoidea does 

 not exceed that of the Atlantic representatives of the genus 

 (Bouchet & Waren, 1980). 



Marshallena gracilispira Powell, 1969, described from Borneo 

 and Philippines, 558-717 m, is probably a synonym of B. 

 trophonoidea; from both original description and figure it is 

 impossible to find any essential characters distinguishing the 

 former species from the latter. However, this question cannot be 

 resolved without an examination of type specimens and more 

 material. 



Distribution. Gulf of Aden, Indonesia, and southern Japan, 

 660-2000 m. The present record is the most western and most 

 deep-sea locality. 



The following species were also mentioned from the John 

 Murray Expedition bathyal samples by A. W.B.Powell (1964, 

 1969) but not found in the material studied: 



Lucerapex denticulata (Thiele, 1925) - Powell, 1964, p. 286 (stn 

 1 76, Gulf of Aden, 732 m; stn 1 84, Gulf of Aden, 1 270 m). 



Nihonia circumstricta (von Martens, 1901) - Powell, 1969, p. 334 

 (stn 1 10, off Pemba Id., 333 m). 



LeucosyrinxjuliaThiele, 1925 -Powell, 1969, p. 338 (stn 34, Gulf 

 of Aden, 1040 m). 



Typhlosyrinx vepallida (von Martens, 1902) - Powell, 1969, p. 

 360 (stn 1 84, Gulf of Aden, 1 270 m). 



Marshallena philippinarum (Watson, 1882) - Powell, 1969, p. 

 369-370 (three stations without numbers indicated, Gulf of 

 Aden and off Pemba Id., 1061, 1022, and 802 m). 



DISCUSSION 



A total of 50 species of deep-sea conoidean gastropods were 

 found in the JME collection. They belong to 3 families, 6 

 subfamilies, 22 genera and 3 subgenera. Lower conoideans 

 (families Drilliidae and Turridae) prevail in the material: 30 

 species vs. 20 in Conidae. Among subfamilies, the most 

 species-rich appeared to be Cochlespirinae (9 species) and 

 Clathurellinae ( 1 1 species). 



The material studied seemingly does not represent well the 

 fauna of the North- Western Indian Ocean; this is evidenced by 

 low percentage of small species and juvenile individuals of larger 

 species as compared, for example to East African bathyal fauna 

 described by Thiele (1925). This is probably due to methods of 

 collection. Additional evidence for this may be the very high 

 share of lower conoideans, often respresented by large species, 

 (60%) which far exceeds the respective values for East African 

 fauna (about 41%, calculated from Thiele's (1925) list) and for 

 other world-wide faunas (Sysoev, 1991). 



Nevertheless, some remarks on the JME collection can be 

 made. The fauna has a typical bathyal appearance, with only few 



representatives of characteristic shallow-water (e.g. Drillia) and 

 abyssal (e.g. Gymnobela (Theta) genera. 



The high percentage of new species in the material studied 

 (about 1/3) indicates that the North- Western Indian Ocean is 

 still insufficiently explored. This is additionally confirmed by the 

 very low overlap with faunal lists obtained by other expeditions: 

 for example, only 5 out of 59 bathyal species reported by Thiele 

 (1925) for East Africa were found in the JME collection (plus 4 

 species recorded by Powell - see above); the same is true for the 

 bathyal fauna of Southern India collected by the 'Investigator' (7 

 species found out of 37 reported by Winckworth, 1940). 



Most species were found at only one station, and thus the 

 main areas covered by the JME investigations (i.e. Gulf of Aden, 

 Zanzibar area, and Maldive Islands) have very few common 

 species: 2 species (Comitas subsuturalis and Gemmula amabilis) 

 were found in all three areas, 2 species (Gemmula bisinuata) and 

 Borsonia symbiophora) - in the two first regions, and one species 

 (Comitas erica) - in the two last. All species also found outside 

 the region studied are apparently widely distributed in the 

 Indo-Pacific. Of particular interest in this connection are the 

 findings which greatly extend the geographic range of respective 

 species: Horaiclavus splendidus previously known from Japan, 

 Leucosyrinx claviforma from North-Western Australia, and 

 Gymnobela daphnelloides from Hawaii. 



Acknowledgements. I am greatly indebted to Dr J.D.Taylor and Ms 

 K. Way of The Natural History Museum, London for the loan of the 

 material and providing relevant information. Dr J.D.Taylor and Dr 

 PMordan of The Natural History Museum kindly edited the 

 manuscript. Of great value were the taxonomic comments of an 

 anonymous referee. I thank Dr Yu.I.Kantor of the A.N.Severtzov 

 Institute of Problems of Evolution of Russian Academy of Sciences, 

 Moscow, for his assistance. 



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