1917] Nomland: Fauna of the Santa Margarita Beds 307 



PECTEN CRASSICARDO BIFORMATIS, n. var. 

 Plate 18, figures 1, la, lb; plate 19, figure 4 

 Type a well-preserved specimen of left valve, no. 11308, from locality 3029, 

 near western boundary of sec 13, T. 32 S, R. 29 E, M. D. B. & M., Tejon Hills, 

 Caliente Quadrangle, Kern County. 



Shell equilateral, equivalve, thin, rather compressed ; with more 

 or less serrate, regularly convex, basal margins. Right valve with 

 about fifteen high, squarish, rather narrow ribs; interspaces consider- 

 ably wider than ribs, both being ornamented by numerous fine radiat- 

 ing lines ; surface sculptured by fine, almost invisible, imbricate lines ; 

 the larger specimens frequently show abrupt constrictions or undula- 

 tions at later stages of growth. Anterior ear ornamented with incre- 

 mental growth lines and about six radiating ridges ; posterior ear 

 smaller but otherwise similar to anterior. Left valve with about 

 fifteen-seventeen high squarish ribs. These are wider than the inter- 

 spaces or than the ribs of the other valve, ornamented with fine 

 incremental lines ; byssal notch well developed. Dimensions of type : 

 Height, 92 mm. ; length, 114 mm. ; length of hinge line, about 65 mm. ; 

 umbonal angle, 110 degrees. 



This species differs from the typical form in having higher and 

 narrower ribs, especially in the left valve, and more compressed sides 

 with abrupt constrictions. 



Occurrence. — Locality 3029, Tejon Hills, Santa Margarita forma- 

 tion ; San Pablo group, Concord quadrangle, Contra Costa County ; 

 Santa Margarita beds, San Luis quadrangle, San Luis Obispo County. 



PERIPLOMA CLARKI, n. sp. 

 Plate 19, figure 6 



Type, no. 11320, in Univ. Calif. Coll. Invert. Palae., from locality 2278, near 

 center of sec. 15, T. 19 S, R. 15 E, M. D. B. & M., about nine miles northeast 

 of Coalinga. 



Shell of medium size, elliptical, thin, with right valve much deeper ; 

 left valve flattened. Umbones small, about three-fourths of length 

 of shell from anterior extremity. Shell rather strongly produced 

 anteriorly, angulated at anterior extremity ; anterior dorsal margin 

 gently convex ; anterior ventral margin with slight angle near middle. 

 Posterior portion of shell short ; some specimens have depression 

 extending from beak to posterior ventral margin, with distinctly 

 biangulate end; posterior dorsal margin slightly convex; posterior 



