GASTEROPODA PECTINIBRANCHIATA. 71 



and widened in its anterior portion, which is distinguished by two 

 deep emarginations. The eyes are on the sides of the tentacula, and 

 near thrirbase. It has neither veil nor operculum*. The 



PURPURA, 



own by its flattened eolmnella, which is trenchant near the end 

 opposite to the spire, and which, with the external margin, forms a 

 e.inal tin iv. Mink in the shell, but not salient. The Purpurae were 

 scattered annum' the Buccina and the Murices of Linna'iis. The ani- 

 mal resemhles tint of a true Buceinnmf. 



The genus LICORNE, Montf., MONOCKROS, Lam., consists of shells 

 similar to the I'urpnra-, but in which the external edge of the emar- 

 gination is furnished with a salient spine];. 



Others, also resembling the Purpura>, in which the columella or 

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

 the aperture, form the SISTRA, Montf., or the RUINULA, Lim. 



CONCHOLEPAS, Lam. 



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

 rinoilB, and tip- *pire so small, that the shell has almost the appear- 

 ance of a Capulus, or one of the valves of the Area; a small salient 

 tooth is visible on each side of the emargination. The animal re- 

 sembles that of a true Buccinnm, with the exception of its foot, which 

 beooriDOiff in width and thickness, and that it is attached to the shell 

 by a muscle sbaped like a horse-shoe, as in the Capuli; it has a thin. 

 narrow, and horny operculum. 



But a single species is known, the Buccinum concholepas, 

 Brug. ; Argenv., pi. ii, f. F, D; and Sowerb., Gen. of Shells, 

 No. VI. From the coast of Peru. 



OASIS, 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 



il, 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 IJneciimm. but its horny opercnlnm is denticulated, in order 



;>s between the plicae of the external margin. 



* Buccinum harpa, L., and the other species long confounded with it List., 992, 

 994; Mart., Ill, r\ix: Bucc. cmfiiti'm, Il>. Messrs. Reynaud, Quoy and 

 Cayman I i,.i\.- observed, that, under certain circumstances, the posterior part of the 

 foot is spontaneously detached. 



cinum p*r.M . 987, 46, 47 ; B. paluhtm, Id., 989, 49 ; B. f"r- 



mastonta, Id., UB8, 48 ; II. w, 1.1., i)(55, 18, 19 ; .U/r.r fuctu, 



I ".0,50; Mur. ill. ci, y/4, 975; J/nr. mancuiclla., List., 



956, 8, 957, 9 10 ; M , List., 955, 996, 990, 991. 



niimo</on, Gm., Martini, III, Ixix. TI'I ; Bucc. narral, Brug. : 11. 



Seb., III. 1\, ::. >:, \2.- ' mlcus, Gm., No. 43. 



