TRIBE CORBTJLACEA. 45 



Sub-orbicular, thick, with thick concentric, rugose, slightly promi- 

 nent ribs, anterior side the shorter, direct and biangulated ; fold 

 distinct ; beaks elevated, yellowish (rarely with faint red rays,) 

 within bright rose red fading into white at the centre ; lateral teeth 

 distinct in each valve. 5. — U. California. 



A. Pulchrum. Sow. Z. P. 1832.— Reeve, t. 47. f. 2.— C. 1. 

 f 2. Oval, pale, finely and concentrically striated : inside mottled 

 with white and purple ; the anterior side the shorter : pos- 

 terior side inclined, somewhat radiatingly striated. L.l^. — 

 S. America. — Not unlike Variegatum in shape. 



A. Ellipticum. Sow. Z. P. 1832. Elliptic, sub-oblique, 

 smooth with slight concentric strise, white under a fuscous epi- 

 dermis, posteriorly longer and rounded, anteriorly shorter and ob- 

 liquely sub-truncated : inside pure white. £ ..2. — W. Columbia. 



A. Punctatum. Sow. Z. P. 1832.— C. I. f. 7. Oval 

 thickish, whitish, with scattered tawny and rosy spots ; anteriorly 

 sub-truncated, with a flexuous fold ; disc with impressed dots, 

 ventral margin with some broad concentric ribs, dorsal spotted with 

 rose at each end. t 6 q . . ly 7 ^. — Gallapagos. 



TRIBE CORBULACEA. 



Inequivalve shells with an interior ligament ; one of the beaks 

 always projecting beyond the other. 



CORBULA. 



Regular, inequivalve, inequilateral, scarcely if at all gaping ; a 

 conical, bent, ascending, primary tooth in each valve ; a small 

 pit at its side ; destitute of lateral teeth; ligament external, fixed 

 in the ligamental hollow. 1 



C. Sulcata. Lam. 2.—E. t. 230 /. l.— Ch f. 1668 to 71. 

 Sub -triangular, very gibbous at the beaks, posteriorly rounded and 

 slightly shorter, anteriorly sub-rostrated, and the slope concave near 

 the broad approximate beaks : whitish under a thin but adhesive 

 brown epidermis ; both valves convex, the larger with strong 

 rounded rather distant transverse ribs, the other simply sulcated. 

 f ..f . — Senegal. 



C. Erythrodon. Lam. 3. Ovate, with transverse grooves ; 

 anteriorly sub-acute, and the more produced ; inner margin pur- 

 plish. 1J. — Peru and Chili. 



1 C. Australis, Lam. 1, is a Saxicava. (Jide Desk.) 



