Clark: The San Lorenzo Series of Middle California 129 



of the ribs; this, however, appears to be due to weathering, not being apparent 

 on the best preserved specimens. Incremental lines rather fine. Cardinal area 

 large, crossed by well-defined multivincular grooves. 



Dimensions. — Type specimen: length, 17 mm.; height, 14 mm.; length of 

 hinge plate, 13 mm. ; length of hinge plate anterior to beak, about 6 mm. 



Occurrence. — University of California localities 52, 1131, etc. Type from 

 locality 52. 



This species very closely resembles A. osmonti Dall, a characteristic 

 species of the Turritella ocoyana zone in the southern part of the 

 state. V. C. Osmont, 102 in his paper on the "Areas of the California 

 Neocene," figured a specimen which he called Area microdonta Con- 

 rad. This was renamed Area osmonti by Dall 103 in his discussion 

 of Area microdonta Conrad. Osmont 's description included two dis- 

 tinct species. The specimen, shown in outline in figures 3a and 3&, 

 of his plate 8, is distinct from the one figured in full, his figures 

 2 and 2b, which is the type of Area osmonti. The other form, out- 

 lined only, appears to agree with Conrad's species Area microdonta. 

 Osmont 's type material is in the University of California collections, 

 therefore the writer has had the opportunity of studying it at first 

 hand. A. submontcreyana is not so large or inflated as A. osmonti 

 and the number of radial ribs is not so great. The type specimen 

 of A. osmonti Dall has twenty-seven ribs; the maximum number on 

 any of the specimens of A. submontereyana examined by the writer 

 is twenty-three. In other respects the two species are quite similar. 



Genus GLYCIMERIS Da Costa 

 GLYCIMERIS BUWALDI, n. sp. 

 Plate 7, figures 10 and 11 

 Type specimen 11150, Coll. Invert. Palae. Univ. Calif., loc. 1131 

 Shell small, subcircular in outline; anterior dorsal slope gently convex; poster- 

 ior dorsal slope short ; posterior end subtruncated. Surface covered by fairly 

 coarse, irregular incremental lines ; also sculptured by numerous obscure radiating 

 ribs, with interspaces which possibly average somewhat less than the width of 

 the ribs ; extending from the beak to the lower angle of the subtruncated end is 

 an indistinct ridge, the narrow margin posterior to which is rather strongly 

 depressed. Hinge plate heavy; cardinal area very narrow; posterior to the beak 

 there are eight, and anterior to it, seven cardinals. A large part of the hinge 

 plate is not covered by the cardinals both below and on the sides ; ventral margin 

 denticulate. 



Dimensions. — Height, 9 mm.; length, 9 mm.; semidiameter, 2.5 mm. 

 Occurrence. — University of California locality 1131. 



Named in honor of Dr. J. P. Buwalda of the Department of Geography of 

 the University of California. 



102 Osmont, V. C, op. ext., p. 90, pi. 8, 1904. 



103 U. S. Geol. Surv., Prof, paper no. 59, p. 110, 1909. 



