TESTACEOUS MOLLUSCA. 275 



compressed, subequilateral; pellucid, very thin, smooth ; ears 

 small, obtusely angulated, the posterior the smaller : lower valve 

 covered with a very thin opaque lamina. 1 . . 1. Greenland. 



P. Latiauritus. Conrad, in J. Ac. N. S. Phil. 7. (including 

 his Mcsotrmeris?) — Sow. Th. f. 20,1. — P. Tunica. Phil. Conch. 

 Pccten. t. 1. /. 3. Obliquely subquadrate, inequilateral, thin, 

 rather flat, anteriorly attenuated ; the ears oblique and costated ; 

 umbones posteriorly inclined; brown variegated with ziczac marks 

 of white or plain orange, with twelve smooth rounded ribs, the 

 interstices concentrically striated. 1-fe* • 1. California. 



P. Tumidus.* Turton Biv. t. 17. /. 3.— Sow. Th. f 27,8,9.— 

 Ostrea T. Turt. C. ID. p. 132. Orbicular, rather compressed, 

 small, thin, smooth ; ears large, nearly equal ; either pale fawn 

 mottled with red and brown, or white or yellow. 0,22.. 0,22. 

 England. This may prove identical with Similis of LasJcey. 



P. Orbicularis. Sow. Th. f. 231,2. Orbicular, inequivalve 

 smooth, thin, nearly equilateral ; ears nearly equal; upper valve 

 ventricose, horn-coloured with a broad submarginal band of dark 

 purplish brown and speckled with lighter brown ; lower valve 

 rather depressed, much lighter, with only light brown speckles ; 

 posterior ear very strongly emarginated. -f ...-^q. Africa. 



P. Hyalinus. Poli t t. 28./. Q.—Philippi. \,p. 80.— Sow. Th.f. 

 66,7, — Orbicular, smooth, hyaline, rather compressed, the sides 

 somewhat expanded ; ears large, nearly equal, acutely angulated, 

 flat; red with small angulated marks of brown and white arranged 

 in rays. Variety. Without spots. \^...\. Mediterranean. 



P. Flagellatus. Lam. 16. — Bel. t. 16. f. 4,7. — Sow. Th. 

 f. 41, 2, 3. Squarish round-shaped, thin, compressed, nearly 

 transparent, irregularly ribbed or striated, horn coloured ; pinkish 

 or yellowish at the sides and auricles, with minute angular marks 

 of white and brown ; ears large and acute. Variety. Blackish 

 brown, -^o• , •4 , Mediterranean. 



P. Glaber. Ch. f. 642,3.— Lam. 20.— Sow. Th. f. 169 to 

 176.— Ostrea G. Lin. 1146.— D. p. 264.— W. t. 10. /. 41.— 

 Knorr. 2, t. 10./. 2. — Including P. Virgo? Lam. Orbicular, rather 

 flattened, smooth or radiately striated, spreading at the sides ; ears 

 nearly equal, broad, acutely angulated; extremely variable in 

 colouring, in those which are variegated the markings angular 

 and defined ; ribs ten, rather rounded, slightly raised near the 

 umbones, flattened so as almost to disappear near the margin, 

 the alternate ones much less elevated. 2... 2^. Mediterranean. 



P. Discors. Chemnitz, f. 2042. P. Proteus. Sow. Th.f. 53,4, 

 83,4.— Ostrea P. D. p. 265.— W. t. 10. /. 42. Subtriangular, 

 compressed, subinequivalve, smooth, or obsoletely striated; ears 



t 2 



