PLEUROTOMA. 231 



PLEUROCERUS. Rafinesque. A genusvery imperfectly described in 

 the " Journal de Physique'' as ' f oval, or pyramidal ; aperture 

 oblong ; outer lip thin; inner lip truncated at the columella , which 

 is smooth and tortuous, not umbilicated. Operculum horny or 

 membranaceous." De Blainville, in giving this description, re- 

 marks that he has neither seen the animal nor the shell of this 

 genus, which he imagines to have been formed from the " Paludine 

 Coupee de M. Say." 



PLEURORYNCHUS. Phillips. (UXevpa, pleura, the side ; puy X oe, 

 rynchus, a beak.) A genus founded upon a very singular species 

 of Carditjm, distinguished by the short anterior side, and the 

 elongation of the hinge line into auricular processes, which are 

 truncated at the extremities. C. Hibernicum from the Black Rock 

 near Dublin, which is vulgarly called Asses-hoof, and C. elonga- 

 tum (Sow. Min. Con. vol. 1. 82.), form part of this genus. 



PLEUROTOMA. Lam. Fam. Canalifera,Lam. Siphonostomata, Bl.— 

 Descr. Fusiform, thick, in general ribbed or striated transversely ; 

 aperture oval, terminating anteriorly in an elongated canal ; outer 

 lip thin, with a fissure near its spiral extremity; columella smooth, 

 nearly straight. Found principally in tropical climates. — Obs. 

 This genus, which nearly resembles Fusus in other respects, may be 

 known by the notch in the outer lip. The species differ in the length 

 of the canal. Swainson has designated this genus a family, thus 

 divided into genera : Brachytoma, in the description of which he 

 says that the spire and aperture are of equal length, including the 

 species strombiformis : Pleurotoma, in which the channel is so 

 much lengthened, as to be little shorter than the spire : Clava- 

 tula, having the long narrow slit of Pleurotoma, but with a very 

 short canal : Clavicantha, having the canal equally short, but the 

 sinus or notch, instead of being linear and long, is short and 

 wide ; the surface is rough, and the whorls either coronated with 

 prickles, or with compressed nodules resembling spines : Tomella, 

 which has the spire and canal fusiform, but the spire of very few 

 whorls, and the inner lip considerably thickened within where it 

 joins the outer lip. Fig. 379, 389, P. marmorata ; 381, P. 

 Strombiformis, (Clavatula, Sw.) 



