TRIBE PECT1NIDES. 271 



(besides some smaller and rather elevated ones at the sides) which 



are narrow and distant, the interstices broad and flat; lower valve 



very ventricose, its margin overlapping the other, its ribs broad 



smooth and without interstices. China, Australia, Zebu, tyc. 

 01 92 



P. Asper. Sow. Th. f. 196,7- Suborbicular, rather com- 

 pressed ; ears broad, obsoletely striated, those of the lower valve 

 serrated at the margin ; upper valve somewhat flattened, slightly 

 elevated towards the umbones ; ribs eighteen, angulated, biangu- 

 lated towards the margin, the angles serrated, and the interstices 

 narrow flat and concentrically striated ; lower valve ventricose, 

 the eighteen ribs rounded, angulated at the umbo, and concentrically 

 striated, the interstices narrow and flat; upper valve pale red, 

 with minute red concentric touches on the ribs and bands in the 

 interstices, these being less numerous in the lower valve (whose 

 ribs are interlineated and the umbo tinted with red) leave it almost 

 white. l^...l^. New Guinea, 



P. iNiEQUivALvis. Sow. Th. f. 193, 4, 5. Suborbicular, rather 

 compressed, oblique, spreading on one side, concentrically striated; 

 ears small and nearly equal ; upper valve somewhat flattened, 

 slightly elevated towards the umbones, grey spotted with blackish 

 brown and black, the eighteen ribs elevated subangulated, the in- 

 terstices narrow and flat ; lower valve ventricose, reddish white, spot- 

 ted with brown on the eighteen elevated and rounded ribs, which are 

 subquadrate near the margin, the interstices narrow and flat, the 

 sides spotted with grey. Variety. Lower valve spotted with red. 

 li. 1^. Philippines. 



P. Aspersus. Sow. Zool. P. 1835.— Sow. Th. f. 198,9 (not 

 Lam.) Suborbicular, rather depressed, subequivalve, equilateral ; 

 the ears unequal, the lower rather large; one valve white or pale- 

 ish, its fifteen ribs larger rounded and smooth; the fifteen more 

 acute ribs in the other, fuscous sprinkled with small bluish dots, 

 the rather pale interstices most delicately striated longitudinally. 

 l T 3 o...l|. Peru. 



P. Nucleus. Born. t. 7. f. 2.— Sow. Th.f. 85.— P. Turgidus. 

 Lam. 15.— Ostrea T. Gmel.—D. p. 268.— -W. t. \\. f. 47.— 

 List. t. 169. f. 6- Orbicular, ventricose, subequivalve, thick, 

 grey clouded with greyish brown, or nearly white clouded with 

 reddish brown ; ribs eighteen to twenty, elevated subquadrate, 

 concentrically striated, the interstices moderate : ears small, 

 nearly equal, grooved, rectangular, l-^...!?. 



P. Circularis. Sow. Z. P. 1835.— Sow. Th.f. 23. Suborbi- 

 cular, tumid, subequivalve, equilateral, variegated with brown and 

 white ; ears large and nearly equal ; radiating ribs eighteen, the 



