270 TESTACEOUS MOLLUSCA. 



P. Fuscus. Klein. — Soiv. Th. f. 118,9. Orbicular ventricose 

 smoth, the upper valve concave at the umbo and rather elevated 

 at the sides, the lower valve very convex at the apex and over- 

 lapping the other valve at the margin ; ears wide rectangular, stri- 

 ated, concave : the ribs fourteen, narrow and nearly square in the 

 upper, wider and rounded with smooth interstices in the lower 

 valve : blackish or reddish brown, the inside clouded with light 

 brown, 3}. . 3±. 



P. Sinensis. Sow. Th. f. 120,1. and 134. Rounded, ventricose, 

 concentrically striated ; light reddish brown, mottled with darker 

 brown, white near the umbones ; ears concave, striated ; the very 

 concave upper valve, with the twelve central ribs, (the lateral are 

 small,) quadrate flattened grooved and narrow, the interstices broad 

 and concentrically striated ; the ventricose lower valve with the four- 

 teen broad rounded ribs grooved obsoletely and longitudinally, the 

 interstices narrow and the margin overlapping the other. 2 T 7 ^. . 3^. 



P. Ziczac. Lam. 5. Sow. Th. f. 129. to 133.— Ch. f. 590,1,2.— E. 

 t. 207. f. 1. — Ostrea Z. Lin. 1144. — D. p. %^{excluding varieties) 

 —List. t. 168 1—Knorr. 2. t. 20. f. l.— W. t. 11. /. 3. Rounded, 

 ventricose, smooth, the ears large, rectangular, with one or two 

 broad slightly raised ribs on the upper part: upper valve flat, 

 with a broad area on each side destitute of ribs ; ribs thirty-one, 

 depressed, alternate, the interstices narrow and most minutely 

 striated : lower valve with twenty-four broad ribs which are obso- 

 lete near the umbo and devoid of interstices ; colour variable, the 

 under valve generally reddish brown softened into purple or white 

 towards the umbones, the upper variegated with white spots, in- 

 terrupted rays of brown and ziczac lines. Red Sea and Phillip- 

 pines, 3 t 3 q . . 3J-. 



P. Dentatus. Sow. in Zool. P. 1835. — Soyv. Th. f. 49. 

 Very inequivalve, equilateral ; ears equal ; the valve flattened, with 

 radiating sulci and striae ; the lower valve very convex, smooth, 

 with radiating sulci, the ventral edge deeply toothed : edge of the 

 upper valve falling deeply within. 3h..3^. W. Colombia. 



P. Erythr^ensis. Sow. Th. f. 163,4. Rounded, ventricose, 

 smooth ; auricles concave and large ; upper valve concave, with 

 nine central ribs, which are concave and distant, three smaller 

 ones on each side; lower valve (which overlaps the other at the 

 margin) with twelve rounded, broad ribs ; yellowish white varie- 

 gated with red, the umbones stained with purple : inside purplish 

 brown. 2...2 T L. Red Sea. 



P. Pyxidatus. Born. t. Q.f. 5. 6.— Sow. Th.f. 24,5.— B. p. 

 268. — Ostrea Sulcata. Gmel. — Ch. f. 604. Inequivalve, or- 

 bicular ; the ears large and nearly equal, with several fine costae ; 

 upper valve flat, hollowed near the umbones, with twenty -two ribs 



