— 56 — 

 FOSSILS DESCRIBED BY OTHERS, NOT FIGURED BEFORE, ETC. 



Pinna alamedensis Yates. (PL IV, Fig. 53.) 



[Report of the State Mineralogist of Calif, for 1887, p. 259.] 

 This species has nine concentric inequidistant rounded wrinkles ema- 

 nating from the open side, and turning toward the hinge at nearly right 

 angles, the entire shell marked by longitudinal narrow ribs (about 

 forty), which, radiating from apex, extend to the basal margin, becom- 

 ing more indistinct as they approach the lower margin. These ribs, at 

 their intersection with the lines of growth, are ornamented by slight 

 elevations, forming zigzag markings along the lines of growth. The 

 hinge side is straight the entire length, the opposite side running par- 

 allel for about one half the distance from base to apex, where it makes 

 a sharp curve, thence at an angle of about forty-five degrees to the apex. 

 Length 9, width 5, and thickness about 2 inches. Locality, Alameda 

 Creek, Alameda County. Only one specimen found, and that a very fine 

 one, in the center of a round sandstone bowlder. Miocene. 



The above is the original description. Specimens have also been 

 found by Dr. Bowers, in Ventura County, and the one here figured was 

 found by Mr. Watts, in Kern County. It retains more of the shell than 

 usually found, most of the specimens being casts. 



Pinna venturensis Yates. (PL V, Fig. 54.) 



[Report of the State Mineralogist of Calif, for 1887, p. 259.] 

 From the hinge side about two thirds of the width of this shell is 

 marked by nine well-developed, narrow ribs, radiating from the apex to 

 the basal margin; the other portion shows rounded, concentric inequi- 

 distant ribs, extending only to the line of the radiating ribs, so that 

 about two thirds of the surface is covered by the radiating smaller ribs, 

 and one third by the curved, concentric, rounded ribs or wrinkles, very 

 like Pinna pectinata, figured in " Brown's Recent Conchology." Pinna 

 venturensis is short and thick compared with its length. The largest 

 specimen found was about five and one half inches long, three and one 

 half in width, and one and three fourths in thickness, the hinge side 

 considerably shorter than the other. Locality, several specimens col- 

 lected by the writer in Casitas Pass, Ventura County. Pliocene. — L. G. 

 Yates. 



This is the original description, and photographs of both the species 

 kindly furnished by Dr. Yates, show that those here figured represent 

 his species. All seen of this species only show the internal cast of the 

 shell, and, as in living species, the external sculpture may have been 

 quite different. There is also but little to distinguish it from the Creta- 

 ceous P. breweri Gabb. 



