CRETACEOUS FOSSILS. 185 



MERETRIX, Lam. 



? M. FRAGILIS, n. 8. 

 PI. 30, Fig. 77. 



SHELL small, extremely thin, elongate; beaks placed about two- 

 fifths of the length from the anterior end, prominent and pointed 

 in advance ; anterior margin excavated under the beaks, broadly 

 rounded below; posterior ends regularly but more narrowly 

 rounded; cardinal margin sloping couvexly; base convex, most 

 prominent under the beaks. Surface marked by concentric 

 striae, in some cases as visible on the cast as externally. Pallial 

 sinus deep, oblique. 



Length, .8 inch ; width, .65 inch ; depth of single valve, .15 inch. 



Rare in the Martinez Group at Martinez, associated with Meekia sella, Pugnellus 

 hamulus, &c. 



Allied in form to M. arata of the Chico Group, but differs in the details of out 

 line, in its marked thinness, and in the surface ornament. 



M. HORNII, Gabb. 



PI. 30, Fig. 78. 

 (Meretriz Hornii, Gabb ; Pal. Gal., Vol. 1, p. 164, pi. 23, fig. 144.) 



As I stated in a note to the description of this species (loc. cit.) the figure in the 

 first volume was not good. I now avail myself of the opportunity of correcting 

 the error by the publication of a more accurate illustration. 



CARYATIS, Roem. 



In a monograph of the Linnaean genus Venus, Dr. Koemer adopts Cytherea, Lam., 

 as a sub-genus, and proposes a "section " Caryatis, to receive a large group of 

 species characterized by a more or less trigonal form ; a shallow or superficial 

 lunule, bordered by an impressed line ; a narrow, subelongate, immersed ligament ; 

 a triangular pallial sinus with an obtuse apex ; a thin, smooth, internal margin ; 

 and with a hinge composed of three divergent cardinal teeth, the anterior thin and 

 direct, the posterior large and oblique, and with a remote posterior lateral. These 

 PAL. VOL. II. 25 



