254 PTEBOCERAS, 



having a spiral band reaching to the centre of each valve. P. 

 terehralis, BL 



PSAMMOBIA. Lam. Fam. Nymphacea, Lam. — Bescr. Trans- 

 verse, oblong, slightly gaping at both ends ; hinge with two 

 cardinal teeth in one valve, one in the other ; ligament sup- 

 ported upon a prominent fulcrum ; muscular impressions two in 

 each valve, sub-orbicular, distant; palleal impression with a 

 large sinus ; epidermis thin. — Ohs. The genus thus described 

 includes Psammot^a of Lamarck, which, according to him, only 

 differs in the number of teeth, and which he says are but " Psam- 

 mobies degeneres." The difference appears to be accidental. 

 This genus differs from TelHna in not having a posterior fold in 

 the margin. PI. iv. fig. 100. 



PSAMMACOLA. Bl. (^pa/jL/ioe, psammos, sand; cola, an inha- 

 bitant.) A name given by De BlainviUe to shells of the genus 

 PsAMMOBiA, including Psammot^a of Lamarck. 



PSAMMOT^A. See Lam. Psammobia. 



PSEUDOLIYA. Sw. A genus of '' Eburnina," Sw. thus 

 described : " Shell thick, oval, oliviform, ventricose : spire very 

 short, acute; base with two parallel grooves, one of which 

 forms a notch at the base of the outer lip ; suture slightly 

 channelled ; inner upper lip very thick, and turning inwards ; 

 aperture vdth an internal canal. Connects the Tuebinellid-s; 

 with the V0LUTIDJ3. P. plumbea, Chem. 188. f. 1806-1807." 

 Sw. p. 306. 



PSILOSTOMATA. Bl. The third family of Aporobranchiata, 

 Bl. containing no genera of shells. 



PTEEOCEEAS. Auct. (Urepov, pteron, a wing ; Kepac, ceras, 

 horn.) Fam. Ailees, Lam. — Descr. Turrited, oval, ventricose, 

 thick, tuberculated, ; spire short ; aperture oval, terminating in 

 a lengthened canal at both extremities ; outer lip thickened, 

 expanded, produced into horn-shaped, hoUow, thickened spires, 

 with an anterior sinus apart from the canal. — Obs. This genus, 

 containing the shells commonly called Devil's Claws, Gouty 

 Scorpions, Spiders, &c. is distinguished from Strombus by the 

 digitations of the outer lip. No fossil species are known. Ten 



