NO. 2134. NOTES ON CHRYSODOMUS—DALL. 225 



Genus ANCISTROLEPIS Dall. 



Ancistrolepis Dall, Proc. U. S. Nat. Mus., vol. 17, 1895, p. 709. Type, 

 Chrysodomus eucosmius Dall, Bering Sea ; Proc. U. S. Nat. Mus., vol. 

 24, No. 1264. 1902, p. 523; Smithsonian Misc. Coll., No. 1727, 1907, 

 p. 157. 



Shell biiccinoid, with the pillar shorter than the aperture, twisted 

 as is usually the canal ; suture channelled ; nucleus beginning with a 

 small initial cell, a blunt apex and followed by regularly increasing 

 inflated, smooth and polished whorls ; the periostracum usually coarse 

 and villous or laminate; operculum straight, concave, fan-shaped 

 with apical nucleus and small area of attachment; penis on a stout 

 stalk with pediform distal extremity without any curved or attenu- 

 ated terminal papilla; radula degenerate and disproportionately 

 small, rhachidian tooth with three long subequal cusps, the laterals 

 with a larger outer and two smaller inner curved cusps. 



All of the species have spiral sculpture, some very strong. None 

 of them has any axial ribbing. In most of them the periostracum 

 is dehiscent and the shell substance white. 



Section JAPELION Dall. 



Shell with a produced spire, a very wide and sharp-edged channel 

 in front of the suture and the periostracum adherent, polished, con- 

 spicuous. Otherwise as in the typical section so far as known. 



Type. — Buccinuin hirasei Pilsbry, 1901. Japan. 



It is a remarkable case of convergence which has brought the 

 typical species of this section to a point where in its specific 

 characters it almost reproduces those of Tritonium pericochlion 

 Schrenck. A casual inspection would hardly distinguish between 

 them, but hirasei has the short pillar of Ancistrolepis while pericoch- 

 lion has a straight long pillar and hardly recurved perfectly distinct 

 canal. It is probable that the latter bears a relation to Colus such as 

 Sulcosipho tahulatus does to Ghrysodomus. But until the soft parts 

 and operculum are known, I refrain from further action. 



There are a number of groups of fossils and a few recent forms 

 which apparently belong to the Chrysodominae, or like Troschelia 

 seem to bridge the gap between this subfamily and the Fusinae. In 

 the absence of authentic specimens it has seemed best in this review 

 to restrict myself to the consideration of the boreal and Arctic forms 

 of which the United States National Museum possesses a quite un- 

 equaled series. 



The position of Sulcosinus will remain undetermined until speci- 

 mens are obtained containing the living animal. Its conspicuously 

 thickened continuous peristome is not paralleled either in the Buc- 

 oininae or Chrysodominae. 



3343— 19— Proc.N.M.vol.54 16 



