2 84 TRIBE PECTIN IDES. 



O. Nucleus (in part.) D.p.2G7. Oval subtriangular, ventricose, 

 equivalve, equilateral, thick ; ears unequal and sulcated, the anterior 

 moderate and straight, the posterior larger and acute : uniform 

 orange, or nearly white with large denned brown patches ; with 

 eighteen nearly smooth elevated squarish ribs, whose sides are most 

 minutely serrated. 1|...1^ . Tranquebar. 



P. Singaporinus. Sow. Th. f. 55 and 71. Rounded subtri- 

 angular, rather compressed, equivalve, equilateral, rather thin ; 

 ears unequal, the posterior large ; white tinged with pink, with four 

 broad brown lineated rays, the twenty-four ribs elevated sub- 

 quadrate and smooth, spotted with grey near the umbones 

 lio«"liV Singapore. A much greater number of less elevated 

 libs than in the preceding. 



P. Senatorius. Lam. 44. — Sow, Th. f. 151, and 188 to 191. 

 — Ostrea, S. Gmel. 3327.— D. p. 256 — W. t. 10, /. 22.— Ch. 

 f. 617.— # t. 211,/. 5.—0. Porphyrea. Gmel.— D.j). 260.— 

 Ch.f. 632.— W. t. 10, /. 30.— P. Aurantius. Lam. 45.— O. 

 Citrina. Gmel.— W. t. 10,/. 23.— D. p. 257 .—Ch. f. 618. — 

 P. Florens. Lam. 46. — Del. t. 15, /. 6. Oval subtriangular, 

 rather depressed, equivalve, nearly smooth, anterior side very 

 slightly spread ; ears unequal, the anterior usually obtuse, the pos- 

 terior elongated and emarginated at the base ; ribs from twenty to 

 twenty-four, rather elevated, smooth or minutely serrated, armed 

 with annular scales which are crowded at the sides : colour ex- 

 tremely variable. 2...HJ. Indies, Moluccas, Red Sea. 



P. Crassicostatus. So?v. Th. /. Ill, 152. Suborbicular, 

 thick, subequilateral, nearly smooth; ears unequal, rayed with 

 squamular ribs ; pale purple or orange, with twenty-four thick ele- 

 vated squarish annulated ribs, the lateral armed with scales, the 

 interstices nearly smooth : white within. 4 1 3 ...4£. Larger than 

 the preceding, with its ribs more square and elevated. 



P. Islandicus. Lam. 42.— Sow. Th. f. 159, 160, 161.— Gould. 

 Mass.— Ostrea, T. Gmel. 3326.— W. t. 10, /. 21.— O. Cin- 

 nabarina. D.p. 256.— Ch. f. 615, 6.—E. t. 212,/. 1. Oval, 

 rather compressed, subequivalve, subequilateral, thin, very slightly 

 spread anteriorly ; ears unequal, with scabrous sulci, the posterior 

 large ; orange with concentric bands, or white or purple with con- 

 centric and radiating bands, the extremely crowded irregular unequal 

 serrated ribs grouped together in twos, threes, or fours. 3\...3. 

 N. Ocean. 



P. Asperrimus. Lam. 43— Del. t. 15, /. 1.— Sow. Th.f. 156, 

 7, 8. — Ostrea, A. W. S. t. 2,/. 1. Rounded snboval, ventricose, 

 thin, equivalve, inequilateral, with scabrous sulci, anteriorly rather 

 spread ; ears unequal, with scabrous sulci; reddish brown, orange, 



