GASTEROPODA PECTINIBRANCHIATA. 377 



t 



at least the margin is provided, in the adult, with teeth which narrow 

 the aperture, form the Sistra, Montf., or the Ricinula, Lam.(l) 



CoNCHOLEPAS, Lam. 



The general characters of the Purpura, but the aperture is so 

 enormous, and the spire so small, that the shell has almost the ap- 

 pearance of a Capulus, or one of the valves of an Arcaj a small 

 salient tooth is visible on each side of the emargination. The ani- 

 mal resembles that of a true Buccin^, with the exception of its 

 foot, which is enormous in width and thickness, and that it is attached 

 to the shell by a muscle shaped like a horse-shoe, as in the Capulij 

 it has a thin, narrow, and horny operculum. 



Buta single species is known, iheBuccinum concholepas,Br\ig.; 

 Argenv., pi. ii, f. F, D; and Sowerb., Gen. of Shells, No. VI. 

 From the coast of Peru. 



Cassis, Brug. 



The shell oval; aperture oblong or narrow; the columella covered 

 with a plate as in Nassa, and that plate transversely plicated, as.well 

 as the external margin; the emargination terminating in a short 

 canal, that is reflected and pushed back, as it were, to the left: 

 varices are frequently observed on it. The animal resembles that 

 of a true Buccinum, but its horny operculum is denticulated, in 

 order to pass between the plicas of the external margin. 



In some, the lip of the margin is denticulated externally near 

 the emargination(2). 



In others it is entire(3). The 



MoRio, Montf. Cassidaria, Lam. 



Was separated from Cassis by Montfort. The canal curves less 

 suddenly, and the whole shell leads directly to certain Murices. The 

 animal resembles that of a Buccinum, but its foot is more develop- 

 ed(4). 



(1) Murex ricinus, L., Seb., Ill, Ix, 37, 39, 42; Mur. neriio'ideus, Gm., No. 

 43, List., 804, 1213. 



(2) Buccinum vibex, Martini, II, xxxv, 364, 365; B. glaucum. List., 996, 60; 

 B. erinaceus. List., 1015, 73. 



(3) The Buccinum of the second division of Gmelin, except the B. echinopho- 

 rum, strigosum, No. 26, and tyrrhenum, which are Cassidariae. It must also be re- 

 collected, that, among the true Cassides, Gmelin appears to have several repeti- 

 tions. 



(4) Buccinum caudatum, L., List., 940, 36; B. echiniphorum, List., 1003, 68; 

 B. strigosiim, Gm,No. 26, List., 1011, Tl, f.; Bucc. tyrrhenum, Bonam., Ill, 160, 



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