272 TESTACEOUS MOLLUSCA 



interstices broader and with curved strife ; the sulci deeper in one 

 of the valves. 1J...1J. St. Vincents and California. 



P. Ventricosus. Sow. Th. f. 18,19,26. — 1\ Tumidtjs. Sow. 

 Z. P. 1835. Subinequivalve, equilateral; ears large and nearly 

 equal, one valve turgid, variegated with reddish brown and whitish, 

 with eighteen radiating ribs which are flattened on the top and 

 have their interstices longitudinally striated ; the other valve more 

 turgid, whitish with radiating sulci ; the interstitial ribs broader 

 and flattened, the lateral variegated with brown : ventral edges 

 acutely dentated. 1-§...1^. W. Columbia. 



P. Irradians. Lam. 37. — Sow. Th. f. 139,140. — Del. t. 15. 

 f. 4. — P. Turgidus. Sow. G. — P. Concentricus. Say. Orbicu- 

 lar, ventricose, rather thin, with minute concentric striae ; ears 

 nearly equal, striated, one side smaller and emarginated at the base ; 

 pale reddish yellow, nearly covered by broad bands and large 

 patches of greyish and reddish brown, a large portion being left 

 nearly white in the lower valve ; the eighteen ribs are rounded, with 

 wide interstices. 3|...3-|. Mediterranean and Newhaven. 



P. Purpuratus. Lam. 11. — Bel. t. 16. f. 5. — Sow. Th.f. 113, 

 123,125. Orbicular, spread at the sides, ventricose, thick; ears 

 nearly equal, with radiating ribs, emarginated at the base; pale 

 purple with strongly marked festoons of white and blackish brown, 

 (a variety also is orange, and even white) on the twenty-two broad 

 flattened ribs, which have their sides serrated, the interstices 

 narrow, with a small serrated rib in the middle, and the margin 

 toothed. 4^-...4|-. Peru. 



P. Gibbus. Lam. 53. — Sow. Th.f. 1, 2, 17, 76.— Ostrea G. 

 Lin. 1147.— D. p. 267.— E. t. 212. /. 3.— Ch.f. 619,0, P— 

 O. Principalis & Flavellum. Gmel. — P. Soverbii. Guilding. 

 Rounded, ventricose, with concentric and radiating striae ; the ears 

 nearly equal, striated and obtuse ; excessively variable in colour- 

 ing, being dull brown, bright red, delicately pink, mottled with 

 brown, light blue variegated with patches of dark brown and 

 touches of white and yellow, with eighteen rather rough ribs : the 

 right valve rather the more ventricose. l-f...]-i^. Pacific. 



P. Operculars. Pen. 4. p. 221. t. 63. /. 2. — Lam. 34. — 

 Philippi. p. 83. — Mont. p. 145. — Sow. Th.f. 141 to 6. — Ostrea 

 O. Ln. 1146.— D. p. 265.— W. t. 11. f. 43.— List. t. 190. 

 /. 27.— E. t. 212. /. 2.— P. Pictus. Da. Cost. t. 9. /. 1,2,4,5. 

 Orbicular, rather ventricose, with concentric and radiating striae ; 

 ears nearly equal, striated, obtuse, one in the lower valve rather 

 the larger and emarginated at the base ; upper valve rough and 

 more ventricose than the other, with eighteen to twenty subangu- 

 lated ribs, with broad interstices; lower valve with the ribs less 

 angulated and the interstices narrower; colour extremely variable, 



