CLASS PELECYPODA 
133 
tenues, modice et sequaliter convexae, iritus subtiliter radiatim striatae, 
epidermide fusca sat conspicua tectae. Long., usque ad 8.5 mm. (Dali.) 
Type in U. S. N. M. Type locality, Arctic Ocean. 
Range. Icy Cape, Arctic Ocean, to Shumagin Islands, Alaska. 
Rochefortia ferruginosa Dali, 1916. 
Proc . U. S. N. M.y 52:411. 
Shell small, white, thin, subdonaciform, compressed, invariably coated 
with a ferruginous layer like some species of Axinuliis, inequilateral; 
anterior side longer, apical angle about 90; both ends rounded base 
arcuate. Length, 4.5; height, 3.25; diameter, 1.5 mm. (Dali.) 
Type in U. S. N. M., No. 214413. Type locality, San Francisco Bay, 
California. 
Range. San Francisco Bay to Santa Rosa Island, California. 
Rochefortia beringensis Dali, 1916. 
Proc. U. S. N. M. f 52:411. 
Shell large for the genus, oval, white with an olivaceous periostracum, 
thin, somewhat compressed, sculptured rudely with low irregular con¬ 
centric ridges; inequilateral, posterior end longer, both rounded; beaks not 
prominent, hinge small and feeble, except that the resilium and its attach¬ 
ments are rather large. Length, 11.5; height, 10; diameter, 4 mm. (Dali.) 
Type in U. S. N. M., No. 210951. Type locality, Bering Island, Bering 
Sea. 
Range. Known only from the type locality. 
Rochefortia grebnitzskii Dali, 1916. 
Proc. U. S.N. M.y 52:411. 
Shell small, translucent, polished, whitish; nearly equilateral; general 
shape that of Bornia, but without the brilliant surface; sculpture of fine 
concentric lines visible under a glass, which render the surface dull; 
beaks rather prominent, hinge weak. Length, 3.25; height, 2.5; diameter, 
1.3 mm. (Dali.) 
Type in U. S. N. M., No. 207258a. Type locality, Bering Island, 
Bering Sea. 
Range. Known only from the type locality. 
Rochefortia aleutica Dali, 1899. 
Proc. U. S. N. M.y 21:892; pi. 87, fig. 6. 
Shell small, solid, ovate, white, smooth covered with a polished straw- 
colored epidermis with usually three or four concentric darker colored 
zones; beaks distinct, often eroded, ends and base rounded, valves moder- 
