140 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
the anterior part longer, rounder, the posterior end more blunt; teeth 
normal, the larger right cardinal nearly parallel with the dorsal margin, 
the ligamentary nymph obscure, the attachment for the resilium thickened 
and projecting; scar of the mantle wide and somewhat irregular, the 
anterior adductor scar not well distinguished from it. Length, 6; height, 
4.2; diameter, 1.5 mm. (Dali.) 
Type in U. S. N. M. Type locality, Monterey, California. 
Range. Known only from the type locality. 
Genus ANISODONTA Deshayes, 1858. 
Shell transversely elongated, compressed, inequilateral; hinge thick; 
a large conical tooth and a triangular socket in each valve; ligament 
external. Anterior adductor scar very small, and comprised between two 
prominent ribs (one parallel and the other transverse to the anterior 
border); posterior scar subcircular, superficial; pallial line faint, entire. 
(Tryon. S. S. Conch.) 
Type. Anisodonta complanatum Deshayes. 
Distribution. Living on the California coast. 
Range in time. Tertiary of Europe. 
Anisodonta? pellucida Dali, 1916. 
Proc. U. S.N.M., 52:411. 
Shell minute, white, pellucid, rounded triangular, smooth and polished; 
beaks prominent, dorsal slopes convexly arcuate behind, straighter in 
front; base arcuate, valves moderately arcuate with entire margins; hinge 
with developed anterior and posterior laterals and two cardinals, the 
anterior tooth bifid. Length, 2.3; height, 2; diameter, 1.3 mm. (Dali.) 
Type in U. S. N. M., No. 208475. Type locality, Monterey Bay, 
California. 
Range. Known only from the type locality. 
Family CHLAMYDOCONCHID./E. 
Genus CHLAMYDOCONCHA Dali, 1884. 
The animal when living is somewhat of the shape of a small globose 
Cyprcca, of inflated ovoid form, translucent, jelly-like, dotted above with 
small, rounded papillae, which appear of an opaque white on the general 
translucent ground. The mantle which covers the dome of the body is 
tough and thick; the sides are smooth, and nearly free from papillae. The 
superior medial line is a little depressed. The basal part of the anterior end 
in life is prolonged beyond the general mass in a wide trough, with the 
convexity upward, and somewhat expanded at its anterior extremity. 
About one-third of the way from the anterior end, the mantle is per- 
