LAMELLIBEANCHIATA OF THE LOWEE MAELS. 143 



little wider at the anterior end than behind. Extremities of the valves 

 nearly equally rounded and the base regularly curved. Cardinal line 

 long behind the beaks, and the margin inflected forming a narrow, linear, 

 escutcheon-like area. Surface of the shell marked by strong and regularly 

 rounded and regularly increasing undulations parallel to the border of the 

 valves. These are crossed by distant radiating ribs, which are strong and 

 vertical in the middle of the valve or opposite the beaks, and become 

 gradually fainter and finer toward the posterior end, apparently becoming 

 obsolete just below the cardinal border, and also before reaching the anterior 

 cardinal margin. These radiating ribs, on the central parts of the shell 

 especially, cut up the surface into rounded nodes by forming depressions 

 across the concentric undulations. Surface of the shell and hinge-structure 

 not seen, as the specimens are all in the condition of casts in a fine mica- 

 ceous marl. 



Mr. F. B. Meek, in his Invert. Pal. U. S. Geol. Surv. Temt, p. 237, 

 cites this species as Cymella bella Conrad, Geol. Rept. North Carolina, 

 Appendix, p. 10, PI. II, Fig. 9. This, however, cannot be, as that species 

 has the radii confined to the central portions of the valves, while in this 

 one they extend over nearly or quite the entire shell. Mr. Conrad states in 

 his description of G, bella that he had the shell itself under examination, 

 which of course would possess the surface marking more completely than 

 would a cast such as these found in New Jersey. These specimens, more- 

 over, correspond in nearly all particulars with those from the Black Hills 

 described in the report of that district. The genus Cymella appears to be 

 very closely related to Pholadomya, and to possess nearly the characters of 

 Poromya Forbes, with which Dr. Stoliczka seems to think is synonymous, 

 while Mr. Conrad thinks it quite distinct. As I have not been able to see 

 the hinge on any of the New Jersey specimens, I cannot give an opinion of 

 its validity. 



Locality and position. — In the fine micaceous marls or clays beneath 

 the Lower Green Sands at Marlborough, Monmouth County, New Jersey, 

 in the collection of the Rev. G. C. Schanck, and from the iron nodules from 

 near Keyport, New Jersey, in the collection at Columbia College, New 

 York. 



