download pdf

MACTRIDAE 447
end smaller than the elliptical posterior end. Shell chalky, dirty-white and
with a coarse, varnish-like, yellowish brown periostracum. Worn shells have
coarse, concentric, wide growth lines. The pallial sinus is larger in this spe-
cies than in solidissima. Moderately common from low-tide line to 60 fath-
oms. The form alaskana Dall is probably a synonym. The fossil, 5. voyi
Gabb 1868 from the Miocene or Pliocene is possibly only a subspecies.
Spisula falcata Gould Hooked Surf Clam
Puget Sound, Washington, to California.
2 to 3 inches in length, rather elongate at the narrower anterior end.
Exterior chalky with a partially worn-off, light-brown, shiny periostracum.
Anterior upper margin of shell slightly concave. Moderately common in
sand below low-water line.
Figure 90. Pacific Surf Clams, a, Spisnla dolabriformis Conrad, 3 inches; b, S.
hemphilli Dall, 6 inches; e, Spistda catiUiformis Conrad, 4 inches; d, Mactra
califomica Conrad, i ^ inches; e, S. pla?mlata Conrad, 2 inches.