DENTALIUM-ANTALIS. 37 



and it must be remembered in dealing with these that an older shell, 

 or a younger one, would show corresponding differences in the 

 sculpture at and near the apex, owing to the truncation of this part 

 with advancing age. 



This species is probably what Carpenter reports as D. tetragonum 

 Sby. from Margarita Bay. 



Another specimen (no. 46207, U. S. Nat. Mus.) before us, from 

 the Gulf of California (pi. 5, fig. 63, apex enlarged), is probably 

 an older stage of this species, in which the apex has been more trun- 

 cated, the riblets extending to the extreme end. There is a short 

 " pipe " for the anal orifice. Length 14*7, diam. at aperture 1*8, at 

 apex 1*3 mill. 



Subgenus ANTALIS H. & A. Adams, 1854. 



Entalis GRAY, P. Z. S., 1847, p. 158, type D. entails. Not Enta- 

 lis Sowerby, 1839, Pyrgopolon Montf. 1810. 



Antalis H. &. A. AD., Gen. Rec. Moll., i, p. 457, examples A. 

 semistriolata Gldg. and A. entalis L. (1854) ; from Antale ALDRO- 

 VANDUS, De Reliquis Animalibus exanguibus, lib. iii, De Testaceis 

 give conchyliis, p. 282 (1642). 



Entaliopsis NEWTON & HARRIS, Proc. Malac. Soc. Lond., i, p. 

 66 (1894), type D. entalis. 



Shell circular or polygonal in section, sculptured with longitudi- 

 nal ribs or striae at least in the young, often without longitudinal 

 sculpture in adults, or only so sculptured near the apex; apex gen- 

 erally with a v-shaped notch at or near the convex side, or with a 

 solid plug and central short tube or orifice. 



Type D. entalis Linn. 



Distribution, Mediterranean, North Atlantic, Arctic and North 

 Pacific. Mainly a group of moderate depths. 



These forms differ from the foregoing ribbed species in the pecu- 

 liarities of the apex mentioned above, which are probably developed 

 in some specimens of all the species, though examples not showing 

 them are also abundant in all. 



The group as here constituted may seem heterogeneous, including 

 as it does species with or without a v-shaped apical notch, with or 

 without a short pipe or tube inserted in an apical plug, and either 

 heavily ribbed or smooth ; but apical characters vary within each 

 species in limits so wide that they are among the secondary specific 

 characters, and they are not correlated with sculptural characters. 



