240 PHORUS. 



PHOLADOMYA. Sow. (Pkolas and Mya.) Fam, Plioladaria, 

 Lam. — Bescr. Thin, rather hyaline, equivalve, inequilateral, ven- 

 tricose, posteriorly gaping, elongated, anteriorly short, rounding ; 

 ventral margin rather gaping ; hinge with an elongated pit, and 

 lateral plate in each valve ; ligament external, short, muscular 

 impressions two in each valve, rather indistinct ; palleal impres- 

 sion with a large sinus. — Ohs. The only recent species of this 

 genus is from the island of Tortola. Several fossil species occur 

 in rocks of the Oolitic series, P. Candida. PI. ii. fig. 57. 



PHOLAS, Auct. (*wXew, pholeo, to lie hid in a cavity.) Fam. 

 Pholadaria, Lam. Adesmacea, B1. — Bescr. Transverse, oblong, 

 equivalve, inequilateral, imbricated, gaping on both sides, the 



• anterior hiatus being generally the largest, although sometimes 

 nearly closed, with the dorsal margin surmounted with one or 

 more laminar accessory valves ; hinge callous, reflected, with a 

 long curved tooth protruding from beneath the umbones in each 

 valve. — Obs. This genus of marine shells, dwelling in holes 

 formed in rocks, wood, &c. is easily distinguished from any other 

 nearly allied genus by the cm-ved, prominent, rib-Hke teeth. 

 The monograph of the family in Pt. 10 of Sowerby's Thesaurus 

 Conchylium contains, besides Tbiomphalia, 42 species. The 

 principal forms of which are represented by Ph. Costata and 



. Candida, Thes. fig. 21, 22, 23, and 8, 9, with one accessory 

 valve. Ph. Dactylus, our fig. 56 (Dactylina) with several acces- 

 sory valves ; Ph. Crispata, Thes. fig. 37. (Zirfcea) with no acces- 

 sory valve. Ph. tridens, Thes. fig. 60, 61 (Calona) with tube. 

 Ph. papyracea, our fig. 56 (Pholadidsea) with a cup-like termi- 

 nation ; and Ph. striata, Thes. f. 40 (Martesia) 'enclosed by 

 various shields. PL ii. fig. 55, 56. 



PHOLEOBITJS. Leach. Part of the genus Saxioata, Auct. 



PHOISTEMUS. Montf. A genus of microscopic Poraminifera. 



PHOEUS, Montf Tkochus agglutinans, &c. Auct. Ee- 

 markable for the adhesion of little pebbles, dead shells, &c. to 

 the outer edge of the whorls, which are taken up in the course 

 of the growth of the shell. Prom this circumstance they are 

 called " Collectors, Carriers, &c." Recent species are brought 



