GASTEROPODA PECTINIBRANCIIIATA. 



365 



Fi£. 130. — Cunchulepas peruviana. 



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



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



observed that, under certain circumstances, the hinder part of the foot is spontaneously amputated.) We recog 



the Purpura, Brug., 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 Muricea 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 SHttra of the former, and the Ricinula of Lamarck. The Concholepas, Lam., baa also the general 



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 



(fiuecinum 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. [The shells are called 



Helmet* b) 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 Mono, Monti'. (Castidaria, 



I.ani.) 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. 



[Oniscia, 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. Strombtu oniseiu, I. inn., is the type of the genus.] Terebra, 

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

 Buccinum, but their spire is drawn out so as tube turriculated or 

 subulate. [The species arc numerous and beautiful.] The Suoiila, 

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

 J the existence of an operculum. 



The Cerithium, Brug., — 

 Dismembered with good reason from the Murexof Linnaeus, 

 i r . lss—cuiidaru «hinop have a shell with a turriculated 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 Potamldei, which, with the rm of shell, i ave ■ very 



ircel) einarginate canal, oo tinus or gutter near the top of the right lip, and the exterior Up dilated. I bey 

 live in rivers, or at least at their months ; and some of them are fossil hi formations where thei ither 



than land or freahn 



Fi|f. 181.— Cassis tuberosa. 



Fl|f. 1R3.— Ccritlicum. 



