428 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



scarcely raised, sculptured all over by numerous, crowded, low, 

 rounded granules, radially arranged and more or less coalescent 

 to form low radial riblets (17-20 on a side ? ), separated from 

 each other by shallow, but quite distinctly cut, sulci. Central 

 areas everywhere sculptured by numerous, more pointed, back- 

 wardly directed, more overlapping granules, which coalesce 

 strongly to form about 55-60 low, granular, longitudinal riblets 

 on each slope, their interspaces about half as wide as the riblets 

 themselves and traversed by a rather weak, transverse thread- 

 ing which shows up more plainly where the tegmentum is 

 slightly worn; riblets more or less oblique on the sides, bending 

 inward as they approach the lateral areas, those nearer the 

 center of the shell becoming straighter, and passing smoothly 

 over the jugal region where they become a little narrower and 

 more numerous than on the slopes. 



Fig. 2. Leptochiton clarki Berry, new species. Anterior elevation of 

 type valve [605] ; camera outline. 



Interior ef valve with a rather strong, anterior, transverse 

 callus. Insertion teeth obsolete. Slits none. Sutural laminae 

 very low, wide, evenly rounded in front, their outer slope only 

 a little more abrupt than the inner and passing smoothly into 

 the lateral margin of the shell. 



Measurements: Caliper measurements of the type are, — 

 long. 2.2, lat. 6.1, alt. 2.6 mm. 



Fig. 3 



Fig. 3. Leptochiton clarki Berry, new species. Dorsal aspect of right 

 side of type valve [605] ; camera outline. 



