60 PALAEONTOLOGY OF CALIFORNIA. 



Also found in the same formation on the shores of San Pablo Bay, west of Mar 

 tinez, and elsewhere. 



Dimensions of various specimens : Length, .55 inch ; width, .52 inch. 



" .49 inch; " .47 inch. 

 " .6 inch; " .57 inch. 



Average depth of valve, .06 to .07 inch. 



This shell belongs to the group (genus ?) Camptonectes, Agas., characterized by 

 a lenticular form, closed all round, edentulous hinge, deep byssal sinus, and the 

 minute radiating sculpture. The species is named after Mr. Peckham, in recogni 

 tion of his valuable services rendered in collecting the fossils found in the vicinity 

 of the Ojai Ranch. 



P. PEDROANUS, Trask, sp. 



(Plaffiostoma Pedroana, Trask; Proc. Cal. Acad., 1856, p. 86, pi. 3, fig. 1.) 

 (P. annulata, Trask; loc. cit., p. 86, pi. 3, fig. 2.) 

 (P. truncata, Trask; loc. cit., p. 86, pi. 3, fig. 3.) 



In 1856, Dr. Trask named three species of Plagiostoma, giving full descriptions 

 and well-executed figures as above. His specimens are casts of a number of dis 

 torted Pectens, perhaps normally a little oblique, but in most cases with the obliquity 

 exaggerated by pressure. They belong, without question, to but one species, and 

 the first name given will have to be retained. I have carefully studied the speci 

 mens, and have visited the locality from which they were obtained. The deposit 

 belongs to the bituminous shale of the Upper Miocene, which underlies the whole 

 or the greater part of the Los Angeles plain, crops out on the beach at San Pedro, 

 under the Post-Pliocene, and has been reached by artesian borings under the city 

 itself. 



The species is about an inch in diameter, ears subequal, shell thin, perhaps nor 

 mally a little oblique, and the shell-substance contains a few concentric undulations 

 or ribs, which are retained in the cast. No specimens show any shell preserved ; 

 so that, if there was any surface sculpture, it is, as yet, unknown. 



OSTREA, Linn. 

 0. VEATCHII, Gabb. 



PI. 17, Fig. 21, 21 a. 

 (O. Veatchii, Gabb; Pal. Cal., Vol. 2, p. 34, pi. 11, fig. 59.) 



This shell was originally described from Cerros Island, whence it was brought 

 by Dr. Yeatch. I have since found it, forming whole beds of Post-Pliocene age, 



