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University of California Publications in Geology [Vol.11 



Only one specimen of this species has so far been obtained. It was 

 found at the locality where Glycimeris tenuimbricata is very abundant. 

 Here G. tenuimbricata is found in rather coarse sandstones while 

 G. b uwaldi was found in a thin layer that might be classed as a sandy 

 mudstone. 



Glycimeris buwaldi is very similar in outline and sculpturing to 

 G. intermedia Broderip, 104 a Recent West Coast species, in fact so 

 much so that the writer would have hesitated to separate the two 

 had it not been that a good hinge plate was obtained on the former, 

 which is quite different from that of the latter. It is heavier ; there 

 is a less number of cardinals ; there is a narrow interspace below the 

 beak between the anterior and posterior cardinals, which is not present 

 on G. intermedia ; also the cardinal area on G. buwaldi is much smaller. 



GLYCIMERIS TENUIMBRICATA, n. sp. 

 Plate 16, figures 4, 8, 9 and 10 

 Type specimen 11183, Coll. Invert. Palae. Univ. Calif., loe. 1131 



Shell subtrigonal, somewhat variable in outline and diameter, medium in size, 

 equivalved, nearly equilateral, valves moderately convex. Apical angle about 

 90°; dorsal slopes straight, the anterior slope being a little the shorter; ventral 

 edge strongly and regularly convex ; posterior dorsal margin, as a rule, slightly 

 more depressed than anterior dorsal margin. Surface sculptured by twenty- 

 three to twenty-nine radiating ribs which become obsolete near the dorsal edges ; 

 ribs separated by interspaces which generally average a little less than their 

 width ; surface also covered by heavy incremental lines which, on unweathered 

 specimens, are very strongly and beautifully imbricated. Hinge plate fairly 

 heavy, with seven or eight teeth anterior to the beak, and ten or eleven posterior 

 to it. The teeth do not reach the ventral margin of the hinge plate ; they are 

 noticeably long and heavy near the ligamental area, which is narrow and ventrally 

 is wedged in between the anterior and posterior rows of teeth ; ligamental grooves 

 numerous and well marked. Muscle impressions equal and fairly heavy. 



Dimensions. — Type specimen: length, 27.5 mm.; width, 26 mm.; paratype: 

 height, 21 mm.; width, 20 mm. 



Occurrence.— University of California localities 14, 513, 1131, 173, 1175, 2754, 

 etc. Type from locality 1131 ; paratype from locality 2754. 



Family Ostreidae 

 Genus OSTREA Lamarck 



OSTREA, sp. indt. 



An imperfect valve of an oyster was found at University of Cali- 

 fornia locality 1131 ; it is determinate generically but not specifically. 

 Two other specimens of Ostrea were found at locality 792; these are 



104 For original description see Proc. Zool. Soc. London, 1832, p. 126; also 

 for description and figures see Conchologia Iconica, vol. 1, pi. 1, fig. 1, 1843. 



