58 PALAEONTOLOGY OF CALIFOENIA. 



SAXIDOMUS, Con. 



S. GIBBOSUS, 11. S. 

 PI. 16, Fig. 18, a, b. 



Shell thin, subquadrate, very inequilateral; beaks anterior, 

 nearly terminal ; anterior end excavated above, narrowly rounded 

 below; posterior end convexly subtruncated, sometimes a little 

 oblique ; base broadly rounded ; cardinal margin gently sloping 

 and slightly convex. Surface marked by small but distinct and 

 somewhat irregular lines of growth. Lunule large, bordered by a 

 very fine impressed line. Hinge, teeth slender. 



Dimensions of two extreme specimens: 1st. Length, 2.3 inch; width, 1.7 inch; 

 diameter of two valves, 1.3 inch ; 2d. Length, 2 inch; width, 1.7 inch; diameter, 

 1.2 inch. 



Common in the Pliocene of Eagle Prairie, Humboldt County. 



Resembles in outline S. Nuttallii and S. gracilis (—aratus), but can be at once 

 distinguished by its smaller size, more gibbous form, smoother surface, and thinner 

 shell. 



YOLDIA, Moll. 

 Y. nasuta, Gabb. 



{Yoldia nasuta, G. Pal. Cal., Vol. 1, p. 216, pi. 32, fig. 287.) 



This shell, described from a single specimen in the Museum of the Cal. Acad. 

 Nat. Sei., has since proven to be undoubtedly Tertiary ; and although the matrix 

 is not. unlike some of the Miocene Shale, underlying the City of Los Angeles, as 

 cut by artesian borings, it seems to me more like the Post-Pliocene deposit near 

 San Pedro. The specimen is labelled "Los Angeles," and its history is entirely 

 unknown. Its lithological characters place it outside of all the known Cretaceous, 

 so that I have little hesitation in making the unqualified statement above. 



