PSAMMOBIA. 237 



appears to be the preferable name, since it has the right of 

 priority over Potamophila. It is found in Africa. 



PRIAMUS. A genus composed of Achatina Priamus, Lam. 

 Buccinum Stercus— Pulicum, Chemn. Conch. 9. t. 120. f. 1026-7. 

 This shell is ascertained to belong to a marine mollusc, having a 

 horny operculum, and therefore is justly considered to form a 

 distinct genus, allied to tbe Buccina and Struthiolarise. Fig. 545. 



PRISODON. Schum. Hyria, &c. Auct. Fig. 144. 



PRODUCED. (Productus, prominent. ) A term applied to the 

 spire of univalve shells, or to any other prominent portion . 



PRODUCTA. Sow. {Productus, produced.) Fam. Brachiopoda, 

 Lam. — Descr. Equilateral, inequivalve, thick, striated ; one valve 

 generally convex, with the margin inflected, produced ; the other 

 valve flat, or slightly convex, with the margin reflected ; hinge 

 rectilinear, transverse.— Obs. The peculiarity of this genus, from 

 which it derives its name, is the manner in which the anterior 

 margins of the valves are drawn out and overwrap each other. 

 The genus is only known in a fossil state. Species occur in 

 Mountain Limestone, and Transition Limestone of older date. 

 P. depressa, fig. 206. 



PROSERPINA. Gray? Fig. 274, represents a small shell be- 

 longing to the Helix tribe, to which it is believed, Mr. Gray has 

 applied the name Proserpina nitida. We do not know how the 

 genus is defined. 



PROTO. Defr. A fossil shell resembling Turritella, but 

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

 terebrans, BL 



PSAMMOBIA. Lam. Fam. Nymphacea, Lam.— Descr. 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. — Obs. The genus thus described 

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

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

 mobies degenerees," The difference appears to be accidental. 



