222 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54. 



Volutopsis Dall, Proc. Cal. Acad. Sci., vol. 5, 1873, p. 57.— G. O. Sars, Moll. 

 Reg. Arct. Norv., 1878, p. 268. — Dautzenberg and Fischer, Res. Camp. 

 Scientifiques de Monaco, 1912, p. 64. 



Shell large, frequently rude or irregular, with the last whorl 

 largest, covered with a thin, inconspicuous more or less dehiscent 

 periostracum ; spire short, blunt, beginning with a relatively large 

 smooth bulbous nucleus; sculpture variable, smooth, spirally striate, 

 or with indistinct wavelike axially directed prominences or even with 

 feeble axial ribs; the aperture ample, the canal short, wide, hardly 

 differentiated. Operculum short-ovate or rounded-quadrate, the nu- 

 cleus at the right anterior corner; dentition: the rhachidian tooth 

 with two to five small cusps, the laterals with two large arcuate cusps. 

 In V. castanea Morch the formula is | : ;^ : | ; in F. norvegica i : i : i, 

 in V. fragilis ^ : i : | according to Sars and Hanna. Ovicapsules 

 large, hemispherical, attached by the whole of the flat side, contain- 

 ing several embryos. The species are boreal and Arctic, especially 

 numerous in the Bering Sea region. 



Having compared the Newfoundland F. Ia7'gillierti with a large 

 series (35 specimens) of the F. norvegica, I am inclined to regard 

 them as distinct though closely related species. Morch's type was the 

 former; in it the nucleus is large, flattish above and with about a 

 whorl and a half. The shell is thin and of an orange tint. In twi^- 

 vegica the enfolding of the apical whorl is almost pointed, and the 

 nepionic shell continues in a subcylindric fashion for three or four 

 whorls. The test is white and heavy. 



In accordance with the International rules for nomenclature, I have 

 returned to the original spelling of the name. 



A feature which is not confined to this genus and which is fore- 

 shadowed in Ancistrolepis is that, while the species like T^. castanea 

 which live in shallow water near shore retain the usual long retrac- 

 tile proboscis and well developed functional radula, other species 

 living in deep water have the radula degenerate in size (F. fragilis) , 

 the proboscis much shortened and the esophagus enlarged. From 

 dissections made by Mr. G. Dallas Hanna under my supervision, these 

 facts have been demonstrated. It seems that these deep water 

 dwellers live chiefly by swallowing quantities of mud containing 

 minute organisms, with which the stomach and esophagus were found 

 loaded. The radula being no longer required and a long proboscis 

 being inconvenient for the purpose, both appear to have degenerated. 

 Something of the sort was noted by me in connection with Ancistro- 

 lepis in 1902, and with an abyssal trochoid mollusk {Turcicula 

 hairdii Dall), in 1889. These adaptations to suit the environment 

 would probably be found on examination of a series of species to 

 gradually merge into one another. 



