SHELLS WITHOUT CANALS 209 



spiral and thin if found in a dead T^egula, and rouf:^h 

 and expanded if exposed to the waves. It may often 

 be found under stones. Farther to the south it is 

 sometimes marked with brown. I have chosen the 

 name n'rccu^ as it conforms to recent usage, though 

 there is excellent authority for combining this species 

 with the next. 



Crepidula lesson?}, Brod., Lesson's Slipper-shell, 

 resembles a long, narrow specimen of the last species. 

 The shell, however, is thickened by a number of 

 layers, partly detached at their edges. The color 

 is white. There is also a short and heavy variety, 

 known as var. explanata, Gould, which some con- 

 sider as a distinct species. 



There is a small species of this extensive genus 

 which has received the name of Crepidula dorsata, 

 Brod., the Wrinkled Slipper-shell. It is nearly cir- 

 cular in outline, thin and flat, with a small, curved, 

 and partially detached deck. This wrinkled brown 

 and white shell is about half an inch across. It is 

 found at points all along the coast. 



Crepidula aculeata, Gmel., the Prickly Slipper- 

 shell, is a small southern form. The yellowish- 

 white shell has a low apex, curved to one side, and 

 its surface is diversified with many irregular radiat- 

 ing ribs. 



Capulus calif orfiicus, Dall, the California Cap- 

 shell, is a recently discovered species, specimens of 

 which are occasionally found in San Pedro Bay, 

 usually clinging to the outside of a large pecten. In 

 shape it resembles a very large Crepidula adunca, but 

 there is no deck inside the shell. Externally it has a 



