116 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Type in U. S. N. M., No. 208948. Type locality, Station 4300, off 
Point Loma, California, in 78 fathoms. 
Range. Known only from type locality. 
Genus CALYPTOGENA Dali, 1891. 
Shell smooth or faintly concentrically striated, with a well-marked 
escutcheon but no lunule; the inner margins smooth; dental formula 
r~ -> 
L.lOlOriO including an anterior lateral in each valve; the teeth become 
R. 0101.01 6 
more or less obsolete in the adult, and in young retain the link between 
laterals and cardinals, which in most bivalves is lost at a very early age. 
(Dali.) 
Type. Calyptogena pacifica Dali. 
Distribution. Pacific, of North America, Fossil, Pliocene Pacific 
North America. 
Calyptogena pacifica Dali, 1891. 
Proc. U. S. N. M. f 14:190 and 17; pi. 25, figs. 4, 5. 
Shell equivalve, elongate, ovate, white with a thick greenish epidermis; 
sculpture of incremental lines; form much like Petricola carditoides 
Conrad, the beaks not prominent, the ligament stout, the escutcheon long, 
narrow, and deep. Length of adult shell, 48; height, 27; diameter, 18 mm. 
The beaks are 14 millimetres behind the anterior end. (Dali.) 
Type in U. S. N. M. Type locality, U. S. Steamer Albatross, Station 
3077, off Dixon Entrance, Alaska, in 322 fathoms. 
Range. Clarence Strait, Alaska, to Santa Barbara Channel, California. 
Calyptogena elongata Dali, 1916. 
Plate 22, fig. 6. 
Proc. U. S. N. M., 52:408. 
Shell resembling a Tagelns in form, elongate compressed, white under 
a yellowish periostracum, rounded at both ends, base nearly straight; 
anterior dorsal slope short, beaks low, small, pointed, about 10 mm. from 
the anterior end of the valves, posterior slope long, gently arcuate; surface 
devoid of any sculpture except rather conspicuous incremental lines; 
ligament strong; interior porcellanous white, pallial line entire; hinge 
teeth small, normal. Length, 44; height, 17.5; diameter, 10 mm. (Dali.) 
Type in U. S. N. M., No. 110774. Type locality, off Point Loma, 
California, in 275 fathoms, at Station 4432. 
Range. Santa Barbara Islands to San Diego, California. 
