GASTEROPODA PECTINIBRANCHIATA. 



365 



Vig. 180. — Cuncliulcpas |je 



foot, pointed behind, widened in front, wnere it is marked with two deep emargmations. The eyes are on the sides 



of the tentacula, near the base. There is no veil nor opercubim. (MM. Reynaud, and Quoy and Gaymard have 



observed that, under certain circumstances, the hinder part of the foot is spontaneously amputated.) 9,\e recoo-nize 



the Purpura, Bru^., by its flattened columella, pointed at the base, and forming there, with the outer lip, a canal 



excavated in the shell, but not projecting-. The species were scattered among- the Buccina and Murices by Lin- 

 naeus. Their snail is like that of Buccinum as now restricted. Some shells similar to Purpura, but in which we 



notice a spine on the outer margin of the canal, form the genus Licorna, Montf. (Monoceros, Lam.) Others in 



which the columella, or at least the lip, is garnished, in the full-grown shell, with teeth that narrow the mouth 



constitute the Sislra of the former, and the Ricimda of Lamarck. The Conr/mli'pas, Lam.. hn< ulsn the ■•cueral 



characters of the Purpura, but the aperture is so 



enormously large and the spire so inconsiderable, 



that the shell has the aspect of a Capulus, or of one 



of the valves of an Area. The emargination of the 



mouth has a small tooth on each side of it. The ani- 

 mal resembles that of Buccinum, excepting in the 



foot, which is enormous in width and in thickness, 



and which is attached to the shell by a muscle in 



form of a horse-shoe, as in Capulus. There is a thin, 



narrow, horny operculum. A species from Peru 



{Buccinum concholepas, Brug.) is the only one known. 



Cassis, Brug. — Shell oblong ; the aperture oblong or 



narrow ; the columella covered with a plate as in 



Nassa, and that plate grooved transversely as well as 



the outer lip : the emargination ends in a short canal, 



which is folded and turned up backwards, and to the 



left. There are often varices. [Tlie shells are called 



Helmets by English collectors, and are in general 



remarkable on account of their great size.] The 



animal resembles that of Buccinum, but its horny 



operculum is toothed, that it may pass between the 



grooves of the outer lip. Some have the varix of this 



lip toothed externally near the emargination ; and 



others have it plain. The Morio, Montf. (Cassidaria, 



Lam.) are separated from the Cassis because their 



canal is less abruptly curved back ; and they lead 



us to certain of the Murices. The animal resembles 



a Buccinum also, but its foot is more developed. 



[Oiiiscia, Sowerby, is sufficiently distinguished 



from Cassidaria by its granulated inner lip, its very 



short, scarcely reflected canal, and its very singular 



general form, which is oblong or subcylindrical, with an obtuse 

 apex. Strojnbus oniscus, Linn., is the type of the genus.] Terehra, 

 Brug., have the mouth, the emargination, and the columella of 

 Buccinnm, but their spire is drawn out so as to be turriculated or 

 subulate. [The species are numerous and beautiful.] The Subula, 

 Blainv., is distinguished by some difference in the animal, and by 

 the existence of an operculum. 



The Cerithium, Brug., — 

 Dismembered with good reason from the Murex of Linnaeus, 

 Kii;. isz.-cassidaria echinophora. havc a shcll with a turriculatcd spire, an oval aperture, and 



a short but distinct canal 

 curved to the left and back- 

 wards. There is a veil on 

 the head of the animal, two 

 distant tentacula, having 

 the eyes at the side, and 

 a round, horny operculum. 

 Many of them are found in a fossil state. 



M. Brongniart has separated from Cerithium the Po/amides, which, with the same form of shell, have a very 

 short, scarcely emarginate canal, no sinus or gutter near the top of the right lip, and the exterior lip dilated. They 

 live in rivers, or at least at their mouths ; and some of them are fossil in formations where there are no other 

 than land or freshwater species. 



Fiir. isi. 



ssis tuberosa. 



