TRIBE CORBULACEA. 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. Putcurum. 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. 1..13, — 
S. America.— Not unlike Variegatum in shape. 
A. Exvurericum. Sow. Z. P. 1832. Elliptic, sub-oblique, 
smooth with slight concentric striz, white under a fuscous epi- 
dermis, posteriorly longer and rounded, anteriorly shorter and ob- 
liquely sub-truncated : inside pure white. ?..2.—W. Columbia. 
A. Puneratum. Sow. Z. P. 1832.—C. J. f. 7. . Oval 
thickish, whitish, with scattered tawny and rosy spots ; anteriorly 
sub-truneated, with a flexuous fold; dise with impressed dots, 
ventral margin with some broad concentric ribs, dorsal spotted with 
6 i (+ eee e 
rose at eachend. °,..145.-— 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. 
C. Surcata. Lam. 2.—E. t. 230. fi.1—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. 
2,.2,—Senegal. 
C. ErytHrRopon. Lam. 3. Ovate, with transverse grooves ; 
anteriorly sub-acute, and the more produced; inner margin pur- 
plish. 11.—Peru and Chili. 

1 C. Australis, Lam. 1, is a Saxicava. (fide Desh.) 
