TRIBE FECTINIDED, 265 
margined with white.—Var. Tinged with violet both externally 
and at the inner margin. 4. Australia. This species is usually 
longer (from the beaks to the ventral edge) than inM. Margaritifera ; 
the nacre of its ear likewise projects more 
Section II. 
Ligament not marginal, inclosed in a short hollow under the beak, 
always perceptible, and not forming a tendinous chord beneath the 
shell. 
TRIBE PECTINIDES. 
Shell for the most part regular and not foliaceous: the ligament 
either internal or partly so. 
PEDUM. 
Inequvalve, somenhat eared: the lower valve gaping; beaks un- 
equal, separate; hinge without teeth ; ligament partly external, 
seated in an elongated hollow in the internal surface of the beaks ; 
lower valve nith a notch near the posterior dorsal margin. 
P. Sronpytoipeum. Lam. 1.—Sow. G.—Reeve. t. 111.—Bl. 
t. 62. f. 6.—Osrrea. S. Gmel. 3335.—D. p. 280.—Ch. f. 669, 
0.—E. t. 178. f. 1 to4.—W. t. 11. f. 75. Ovate wedge-shaped, 
fiat, whitish, slightly tinged with violet towards the beaks ; epider- 
mis ferruginous: upper valve the larger, roughened by longi- 
tudinal undulated granular striz. Var.? Smaller and rounded, 
the lower valve the flatter. 3. Mauritius § Indian Ocean. 
LIMA. 
Longitudinal sub-equivalve, with small ears ; valves slightly gaping 
on one side ; beaks separate, their inner surface sloping outwards ; 
cavity for the ligament partly external ; hinge without teeth. 
L.Scasra. Sow. Th. p. 83. t. 21. f. 4,5, 12.—Osrrea. S. 
Born Mus. Ces. p. 110.—W. t. 11. f. 55.—D. -p. 271.—O. Graci- 
ais. Gmel.—Percten AspEra. Ch. f. 653.—Lima G. Lam. 3.— 
Son. G. f. 1.—Reeve Sys. t. 112. f. 1.—E. t. 206. f. 2. Oval, 
thick, rather compressed, slightly gaping at the anterior margin, 
rather more so at the posterior; surface rendered scabrous by an- 
gularly notched ribs meeting in the centre at an angle: ears striated 
the posterior tumid and slightly reflected : epidermis brown ; hinge 
thick and obsoletely plaited. Sometimes this species becomes wregu- 
larly tongue shaped. 1,40..2. W. Indies. 
