86 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Cyathodonta dubiosa Dali, 1915. 
Plate 9, fig. 5. 
Proc. U. S. N. M., 49:445. 
Shell in general resembling C. undulata on a smaller scale. The left 
valve is nearly as convex as the right valve. The plaits are less regular, 
becoming obsolete behind and toward the basal margin. The left valve 
has only two very faint rays, the right valve also two, of which the 
dorsal one is strong. The granulation is in somewhat irregular concentric 
lines and not radially distributed; the pallial sinus is not so high relatively 
and falls short of reaching the vertical of the beaks. Length, 38; height, 
29; diameter of right valve, 9; of left valve, 7 mm. (Dali.) 
Type in U. S. N. M., No. 96450. Type locality, off La Paz, Lower 
California. 
Range. San Pedro, California, to the Gulf of California. 
Cyathodonta pedroana Dali, 1915. 
Plate 54, figs. 1, 2, 3. 
Proc. U. S. N. M., 49:445. 
Shell small, white, resembling C. dubiosa but more pointed behind, 
hardly truncate, anterior end longer; valves nearly equally convex; the 
plaits are more numerous (±25), narrower, more close-set and more 
regular; they reach the posterior dorsal margin; the rays are obscure; the 
ganulations obscurely, concentrically disposed; the sinus is small, shallow 
and does not reach the vertical of the beaks. Length, 27; posterior end 
to vertical, 10; height, 21; diameter of right valve, 6; of left valve, 5 mm. 
(Dali.) 
Type in U. S. N. M., No. 207527. Type locality, San Pedro Harbor, 
in mud. 
Range. San Pedro Harbor and Catalina Island, California. 
Genus ASTHENOTH2ERUS Carpenter, 1864. 
Shell like a Thracia, hinge without teeth, spongy cartilage situated in 
a pit under the umbos. 
Type. Asthenotluerus villosior Carpenter. 
Distribution. California to Cape San Lucas, Lower California. 
Asthenothaerus villosior Carpenter, 1864. 
Ann. Mag. Nat. Hist., (3) 13:311. 
Testa inaequivalvi, imequilaterali, umbonibus ad trientem longitudinis 
sitis; tenuissima, alba (sublente), omnino minutissime et creberrime 
pustulosa; rugis increment! obtussimis, irregularibus, maxime t. juniore, 
