POTAMOPHILA. Sow. ([Greek: Potamis], _potamis_, river; [Greek: philios], _philios_, choice.) "Conques fluviatiles," Lam.--_Descr._ Thick, equivalve, inequilateral, trigonal, covered with a greenish brown, smooth, horny epidermis; hinge thickened, broad, with one central, notched cardinal tooth in one valve, and two in the other, with indistinct lateral teeth; ligament large, supported on prominent fulcra; muscular impressions two in each valve, sub-orbicular.--_Obs._ The name given to this shell refers to its place of abode, being found in rivers. It is the Venus sub-viridis of some authors, although being a fresh-water shell, and having an incrassated hinge, and a smooth, thick epidermis, it is most distinct from that genus. It is described by Bowdich under the name Megadesma, on account of its large ligament, and by Lamarck under that of Galathæa, a name previously used by him for a genus of Crustacea. P. radiata, fig. 115. Megadesma 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 the Buccina and Struthiolariæ. 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 belonging 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. terebralis, Bl.