CRETACEOUS FOSSILS. 185 



MERETRIX, Lam. 



? M. FRAGLLIS, n. S. 

 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 convexly; 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, hut differs in the details of out- 

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



M. Hornii, Gabb. 



PI. 30, Fig. 78. 



{Meretrix Hornii, Gabh ; Pal. Gal,, Vol. 1, p. 164, pi. 23, fig. 144.) 



As I stated in a note to the description of this species (Joe. 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. Roemer adopts Cytherea, Lam., 

 as a sub-genus, and proposes a "section" Caryaiis, 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 



