380 MARINE INVERTEBRATES 



of Dolium, except that it has two side-flaps, which, when extended, 

 partially inclose the shell. The shell is thin, with an almost flat spire 

 and a greatly enlarged body-whorl. The aperture is flaring, and is 

 drawn out anteriorly into a tapering canal, which gives to the shell the 

 outlines of a pear. The ornamentation is revolving, but not highly 

 raised, and there are ribs with very distinct longitudinal lines of growth 

 between. The color is pure white, or sometimes yellowish, with rufous 

 spots ; within it is golden. This attractive shell is usually from three 

 to four inches in length, but is sometimes found considerably larger, 

 (Plate LXXI.) 



FAMILY CASSIDID.K 



The cassides, commonly known as the " helmet-shells," are car- 

 nivorous mollusks, which lead an active life in sandy stations, 

 prowling about in search of bivalves, upon which they prey. 

 They have a large siphon and a fairly large and extensible pro- 

 boscis. The foot is broad and strong, being well adapted for plow- 

 ing through the sand. The shell of Cassis is large, generally 

 heavy and inflated, with a short spire and a short, recurved ante- 

 rior canal. The lip is much thickened. Upon the Atlantic coast 

 of North America there are four species of Cassis. They are all 

 properly West Indian in their faunal relations, but have found 

 lodgment on the American shore at various points. All of them 

 have been taken in the neighborhood of Cape Hatteras, two of 

 them in West Florida, and two in Texas. 



C. tuberosa. A large, heavy shell, often from six to eight inches in 

 length, with a flattened spire. The aperture is long and narrow, with 

 large white teeth upon the outer lip, which is also greatly thickened. 

 The columellar lip is ribbed. A heavy deposit of enamel to the left of 

 the columellar lip gives the shell a triangular outline. A row of very 

 large nodes upon the shoulder of the body-whorl and two rows of obso- 

 lete nodes below are characteristic features of this species. The color is 

 light yellowish-brown suffused with pink. The aperture and the columel- 

 lar callosity are flesh -tin ted, with chestnut trimmings. The anterior canal 

 is deep and recurved. 



C. cameo. A species of about the same size as the last, but more 

 ovate or ventricose in form. It is coarsely striated, with elevated growth- 

 lines, and has circling rows of large, rib-like elevations, having some- 

 times nodes upon the body-whorl. The columella is conspicuously 

 ribbed and greatly expanded. The outer lip is thickened, and has 

 lamelliform teeth within. Flesh-colored ; teeth white ; purple-brown 

 trimmings. A great many of these shells are sent yearly from Nassau 



