OF CONCHO LOGY. 119 



therefore they cannot be congeneric. Having compared the 

 operculum of the different species with that of M. brevialis, as 

 figured by the Messrs. Adams, I can detect no difference, except 

 that the latter is slightly concave while the former are flat, or 

 nearly so. This can hardly consitute a generic difference; the 

 whorls of the operculum offer no special differences, though 

 Adanson's figure represents a distinct siphonal fasciole which is 

 not seen in other figures of M. brevialis, and does not exist in 

 any of the species I have examined. 



Specimens of the reticulata and polaris were obtained by me 

 at Plover Bay, E. Siberia, in 1865 — 6. 



TRICHOTROPIDiE. 



TRfCHOTROPIS, B. and S. 



Subgenus Iphinoe, H. and A. Ad. 



Iphinoe permabilis, n. s. 



Shell globose, of four whorls, covered with a yellowish vel- 

 vety epidermis, translucent white. Spire slightly elevated, with 

 two carinse on the upper whorls ; (nucleus eroded ;) last whorl 

 with six regular, equidistant, revolving ribs or carinse rounded 

 on top, and in a fresh state furnished with squarish transverse, 

 minute prolongations of the epidermis. Upper surface of the 

 whorl, between the suture and the first carina, subtabulate, 

 transversely striate ; suture channelled, very narrow. Aperture 

 nearly two-thirds as long as the shell, sharply angulated below 

 and above. Outer lip roundly arcuated, thin, sharp. Inner lip 

 smooth, not callous. Columella reflected, straight. Umbilicus 

 pierced, not large, sharply carinated behind. 



Lon. -5 ; lat. -34 in. ; defl. 80°. 



Habitat. — One living specimen in four fathoms mud and shell, 

 North Harbor, Unga Island, of the Shumagin group. 



This pretty little species is very close to Iphinoe dolium, 

 Petit, from Spitzbergen, but is much less elevated and acute, 

 with more tabulate whorls and a much smaller umbilicus. The 

 columella of Petit's species is also oblique instead of straight, 

 and the shell is much larger, with the same number of whorls. 



Trichotropis bicarinata, Sby. 



Under this name several forms appear to have been con- 

 founded, though the material at hand is insufficient for a thor- 

 ough differentiation of them. The typical form described by 

 Sowerby in the Tankerville Catalogue, and also figured there, is 



