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 



calif omica Conrad, i ^ inches; e, S. pla?mlata Conrad, 2 inches. 



