PLETJEOTOMA. 247 



PLETJROCEEUS. Eadfinesque. A genus very imperfectly de- 

 scribed in tlie " Journal de Physique" as " oval, or pyramidal ; 

 aperture oblong ; outer lip thin ; inner lip truncated at the 

 columella, wliich is smootb and tortuous, not umbilicated. Oper- 

 culum borny or membranaceous." De BlainviUe, in giving this 

 description, remarks that be bas neither seen the animal nor tbe 

 sbeU of tbis genus, wbicb be imagines to bave been formed from 

 tbe "Paludine Coupee de M. Say." 



PLEUEOETNCHIJS. PbiUips. (UXevpa, jileura, the side; pvyxog, 

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

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

 elongation of the binge line into auricular processes, which are 

 truncated at the extremities. C. Hibernicum from the Black 

 Eocknear Dublin, wbicb is vulgarly called " Asses-hoof," and C. 

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

 PI. xxiv. fig. 505. 



PLETJEOTOMA. Lam. Fam. Canalifera, Lam. Sipbonostomata, 

 Bl. — Bescr. Eusiform, thick, in general ribbed or striated trans- 

 versely ; aperture oval, terminating anteriorly in an elongated 

 canal ; outer lip thin, with a fissure near its spiral extremity ; 

 columella smooth, nearly straight. Pound principally in tropical 

 climates.— OS*. This genus, which nearly resembles Eusus in 

 other respects, may be known by the notch in tbe outer lip. Tbe 

 species differ in the length of the canal. Swainson bas designated 

 tbis genus a family, and divided it into tbe following 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 : Clavatula, having the long narrow slit 

 of Pleurotoma, but with a very short canal : Clavicantha, having 

 tbe canal equally short, but the siaus or notch, instead of being 

 linear and long, is short and wide ; the surface is rough, and tbe 

 whorls either coronated with prickles, or with compressed nodules 

 resembling spines : TomeUa, which has the spire and canal fusi- 

 form, but tbe spire of very few whorls, and tbe inner lip con- 

 siderably thickened withia where it joius the outer lip. Eig. 379, 

 389, P. marmorata; 381, P. Strombiformis, (Clavatula, Sw.) 



