80 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Crenella leana Dali, 1897. 
Bull. Nat. Hist. Soc. Brit. Col., 2:4; pi. 1, figs. 6, 7. 
Shell small, plump, ovate, nearly smooth, with a brilliantly polished 
olivaceous epidermis; beaks prominent, terminal; sculpture of delicate, 
concentric incremental lines, which at irregular intervals are sharply im¬ 
pressed, crossed by obsolete radial striae which are hardly perceptible 
except on the beaks, near the margin of the valves and at the impressed 
lines; margin of the valves microscopically dentate; ligament sub-internal, 
inconspicuous; hinge line thickened below the beaks and perceptibly, 
minutely dentate; muscular impression ovate, rather large; interior of 
the shell obscurely pearly. Extreme length, 5; height, 3.5; diameter, 
3 mm. (Dali.) 
Type in U. S. N. M. Type locality, near Middleton Island, Alaska. 
Range. Aleutian Islands, eastward to Middleton Island, Alaska. 
Crenella Columbiana Dali, 1897. 
Plate 15, fig. 4. 
Bull. Nat. Hist. Soc. Brit. Col., 2:4; pi. 1, figs. 3, 5. 
Shell large for the genus, inflated, elongate, oval, thin, of a delicate 
greenish-gray tint, usually somewhat stained by blackish blotches; umbos 
conspicuous, prosogyrous, terminal; surface of the shell entirely covered 
with fine radiating threads, like those of C. decussata, but proportionately 
more delicate; concentric sculpture, only of delicate incremental lines; 
margin of the valves extremely thin and minutely denticulate; a small 
portion immediately under the beaks thickened; ligament rather long, deep- 
seated, hardly visible externally; interior pearly, the muscular and pallial 
impressions hardly visible, close to the margin. Extreme length, 16; 
height, 12; diameter, 9.5 mm. (Dali.) 
Type in U. S. N. M. Type locality not stated. 
Range. Aleutian Islands to San Diego, California. 
Crenella grisea Dali, 1897. 
Plate 3, fig. 1. 
Smithsonian Misc. Coll., 50:406. 
Shell thin, oblique, elongate, rounded-quadrate when adult, the young 
specimens relatively shorter; surface of a grayish olivaceous color, with 
lighter and darker zones, brilliantly polished, with faint, irregular traces 
of fine, obsolete, radial striation; beaks inconspicuous, hinge line gently 
arcuate, with a minutely denticulate small lamella directly under the beaks ; 
the margin behind the beaks with narrow internal elongate ligament, 
behind which are sharp, minute, interlocking denticulations of the margin. 
