192 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
This was described as a Spisula by Conrad. 
Type locality, Panama. 
Range. Lobitas, California, to Panama. 
Mactra californica Conrad, 1837. 
Plate 20, figs. 4, 5, 6. 
Jour. Acad. Nat. Sci. Phila. 7:240; pi. 18, fig. 12. 
Shell triangular, compressed, equilateral; posterior margin rectilinear, 
posterior side with a carinated, rectilinear, sub-marginal line, beaks promi¬ 
nent, sulcated; epidermis brown, with concentric wrinkles; teeth lamellar, 
large, very prominent. (Conrad.) 
Type locality, Santa Barbara, California. 
Range. Neah Bay, Washington, to San Diego, California. 
Mactra nasuta, Gould, 1851. 
Proc. Boston Soc. Nat. Hist., 4:88. 
T. solida, transversa, ovato-cuneata, albida; epidermide stramineo 
postice incrassato et fuscato induta; vertice fere mediano, acuto; latere 
antico angutato, compresso, sub-adscendente; latere postice dilatato, trun¬ 
cate, hiate; area dosali postica lanceolata, excavata; intus polita, Candida; 
fovea ligamentali perobliqua; dente V-formi tenui, elongate; dentibus 
lateralibus crassis. Long., 3% ; lat., 1; alt., 2poll. The analogue of 
M. brasiliana, distinguished by the posterior portion of the beaks, and the 
more attenuated form of the anterior half caused by the concave outline 
of the dorsal margin. The parts composing the hinge are more oblique. 
(Gould.) 
Type locality, Mazatlan, Mexico. 
Range. San Diego, California, to Mazatlan, Mexico, and West 
Colombia. 
Genus SPISULA Gray, 1838. 
Shell small, subequilateral, trigonal, with a thin epidermis, adjacent 
beaks, and concentrically grooved dorsal areas; pallial sinus small, 
rounded; gape obsolete; valves convex; ligament sigittate, set in a 
callous area close to the dorsal margin and not set off from the chondro- 
phore by any shelly ridge; dental armature normal, strong, not concen¬ 
trated; the opposed surfaces of the laterals transversely grooved; left 
cardinal small, prominent, with a small posterior accessory lamella, the 
posterior ends of both projecting over the chondrophore; right cardinal 
with the arms coalescent above, the anterior arm close to the dorsal shell- 
margin; hinge plate thick and flattish; exterior smooth or concentrically 
striated; the dorsal areas ill-defined. (Dali.) 
