CRETACEOUS FOSSILS. 197 



NUCULA, Lam. 



N. (Acila) truncata, Gabb. 



(Nucula truncata, Gabb; Pal. Cal., Vol. 1, p. 198, pi. 2G, fig. 184.) 



A very common species, found at almost every locality of the Chico, Martinez, 

 and Tejon Groups. The specific identity of these fossils having been denied, I 

 have re-investigated the subject with the utmost care, and have failed to find even 

 a varietal difference between specimens from the three deposits. At the same 

 time, in the Martinez Group, at Martinez, in addition to the normal form, and 

 associated with it, is a larger variety, of which I have three specimens. These I 

 have compared, with the assistance of Mr. Conrad, both with the smaller variety 

 of the Martinez Group, and with others from the adjoining deposits, and we can 

 find no difference except the size. 



N. SOLITARIA, 11. S. 

 PL 32, Fig. 94. 



Shell small, rounded triangular; beaks small, rather promi- 

 nent, subterminal, and inclined forwards ; cardinal margin nearly- 

 straight, rapidly sloping posteriorly; anterior end subtruncated, 

 a little excavated under the beaks, and very slightly convex below, 

 united with the base by a pretty well-marked angle ; base rounded, 

 most prominent a little behind the middle; posterior end narrowly 

 rounded. Surface marked by a few large and many minute lines 

 of growth ; hinge robust, pit small. 



Length, .26 inch ; width, .22 inch; height of single valve, .04 inch. 



Very rare in the Chico Group, Texas Flat, Placer County. 



With the general form of N. (Acila) truncata, this shell is very much smaller, 

 and the entire absence of the radiating ornament will at once distinguish it. It 

 is wider from beak to base in proportion to its length, the anterior end is much 

 more convex, and the posterior is somewhat narrower. 



LEDA, Schum. 

 L. Gabbii, Con. sp. 



(L. protexta ? Gabb; Pal. Cal., Vol. 1, p. 199, pi. 26, fig. 185.) 



(Not L. V rotexta, Gabb; Jour. Phil. Acad., 2 Ser., Vol. 4, p. 303, pi. 48, fig. 23.) 



(Nuculana Qabbii, Con. ; Smithsonian Check List, No. 44.) 



