54 PALAEONTOLOGY OF CALIFOKNIA. 



CLIDOPHORA, Cpr. 



C. PUNCTATA, Coil. Sp. 



PL 15, Fig. 12. 



{Pandora punctata, Con. Jour. Phil. Acad., 1 S. Vol. 7, p. 228, pi. 17, fig. 1.) 

 (Clidophora punctata, Cpr. Proc. Zool. Soc., Lond., 18G4, p. 598.) 



A shell having all the characters of this species in size, form, &c, except the 

 punctations, was found by Mr. Samuel Peckham in the Upper Miocene bituminous 

 shale, in the "Wheeler Canon," near San Buenaventura. The valves are in con- 

 tact, but the inner layer is in part exposed. The closest scrutiny on the outside of 

 this layer fails to disclose the pits considered so characteristic of Mr. Conrad's 

 species ; nor do they show themselves on the marginal one-quarter of an inch of 

 the inner surface which I have succeeded in uncovering. 



HEMIMACTRA, Swains. 



? H. OCCIDENTALIS, 11. S. 



PL 15, Fig. 13, 13 a. 



Shell thin, subovate, inequilateral; beaks small, closely ap- 

 proximating, placed about two-fifths of the length from the ante- 

 rior end, which is broadly excavated above, and prominently, 

 though narrowly rounded below; posterior end convexly and 

 obliquely sub-truncated; cardinal margin sloping and nearly 

 straight ; base broadly and regularly convex ; a moderately dis- 

 tinct angle runs from the beaks to the posterior basal margin. 

 Surface covered by small but moderately prominent and pretty 

 regularly placed lines of growth. 



Length, 2.7 inch; width, 2.2 inch; diameter, 1.2 inch. 



From the Miocene south of Martinez. Bare. A single specimen in my collec- 

 tion, obtained by Mr. Mathewson. 



This shell resembles none of the West Coast Mactroids in form. It has not the 

 extremely inequilateral and subcircular outline of the Miocene lenticularis, Nob., 

 nor the trigonal shape of all the Standellas. I can only refer it provisionally to 



