130 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
visible; from the beak extends a wide depression obliquely backward to 
the middle of the base, becoming more defined distally; at the base in the 
adult it is strongly marked and emphasized by a rounded sulcus in the 
margin, behind which the surface rises into a rounded ridge armed with 
one or more elevated short lamellae, and having its basal termination pro¬ 
duced into a short hook; hinge rather feeble, valves rather compressed. 
Length, 6.3; height, 4.5 ; diameter, 2 mm. (Dali.) 
Type in U. S. N. M., No. 225192. Type locality, off South Coronado 
Island, Lower California. 
Range. Known only from the type locality. 
Erycina balliana Dali, 1916. 
Proc. U. S. N. M. t 52:410. 
Shell small, with the outline of a very compressed Kellia, white with 
a very pale yellowish periostracum, concentrically microscopically 
threaded, the threads occasionally becoming microscopically lamellar; 
valves nearly equilateral, the anterior part slightly longer, base evenly 
arcuate, the posterior end somewhat attenuated. Length, 3; height, 2.9; 
diameter, 1.7 mm. (Dali.) 
Type in U. S. N. M., No. 225191. Type locality, off South Coronado 
Island. 
Range. Known only from the type locality. 
Erycina chacei Dali, 1916. 
Proc. U. S. N. M., 52:410. 
Shell small, compressed, rounded-quadrate; nearly equilateral, the 
anterior end slightly shorter; beaks low, pustular, minute; dorsal margin 
nearly straight, basal margin gently arcuate; surface finely concentrically 
striate, whitish under a pale ashy periostracum, both ends nearly evenly 
rounded, hinge very feeble. Length, 5.3; height, 3.5; diameter, 1.8 mm. 
(Dali.) 
Type in U. S. N. M., No. 211219. Type locality, Station 4343, off 
the South Coronado Island, in 155 fathoms. 
Range. Santa Rosa Island, California, to the Coronado Islands, 
Lower California. 
Erycina santarosas Dali, 1916. 
Proc. U. S. N. M., 52:411. 
Shell small, compressed, whitish, with a thin pale brownish dull 
periostracum; profile approaching E. balliana but more elongated, and the 
surface smooth, almost polished and without the microscopic concentric 
sculpture; evenly ovate equilateral, the anterior end a trifle shorter; beaks 
