36 
Lam, 6.—Pellucid, fragile, rounded at both ends, hinge 
margin nearly straight, the ventral slightly curved : 
a single tooth in one valve and two in the other, besides 
contiguous lateral processes. 4...1. Sandy bays. 
S. Lecumen, Lin. 1114.—D. p. 61.—Lam. 11.— 
Ch. f. 32,3, 4—Don. t. 53.—Pen. 4. p. 84. ¢. 46. 
J. 24.—Mont. p. 50.—F. p, 459.—Psammosia. L. 
Turt. B. p. 90.—Linear, rounded at both ends, hinge 
margin nearly straight, ventral edge slightly curved so 
as to render the posterior end the narrower; smooth, 
yellowish, thin, pellucid, with fine lines of growth; 
hinge strengthened by an oblique internal rib, a single 
tooth in one valve and two in the other, besides lateral 
teeth which are simple in one valve and winged at the 
other. 3...4. Ireland and Wales, common. 
S. Coarctatus. Gmel. 3227.—D. p. 64.—Lam. 
17.—Ch. f.45.—S. Antiquatus.Lam. 15.—Mont. 
p.52.—PsammMoBia. A. Turt. B. p. 91.—F. 460.— 
S. CuLtTe.ivus. Pen. 4. t. 46. f. 25.—S. CEeNTRALIs. 
Say. (fide Jay).—Oblong, rounded at the extremities, 
hinge margin slightly convex, ventral rather concave ; 
white, subpcellucid, merely striated by the lines of 
growth, which are more conspicuous at the extremities ; 
