488 PALiEONTOLOGY OF NEW- YORK. 



Caiiiai'iiiiii duii<>'atuiii (n.s.)- 



Plate XCV A. Fia. 4. 



Shell elongato-ovate, somewhat ventricose. Ventral valve convex, most 

 gibbous on the umbo, having a broad low subangular prominence along 

 the middle to near the front of the valve, which is slightly produced 

 and little elevated : beak produced, slightly incurved ; umbonal ridges 

 rounded ; foramen, large, triangular. Dorsal valve unknown. 



The interior of the ventral valve has a broad and deep rostral cavity ; 

 transverse septum much elongated, extending considerably beyond the 

 middle of the valve, and embracing about one-half of the transverse 

 diameter. The ridges which rise from the bases of the dental plates 

 diverge and pass outside of the transverse septum, sometimes leaving 

 a deep and narrow channel between them. 



This shell diifers from C. typum in being more elongate and- less ventricose, and 

 in having the beak as well as the front less abruptly curved : the transverse septum 

 is proportionally narrower, and extends farther along the valve; while the ridges of 

 the dental plates do not unite with the septum, but pass along the outside of its 

 base. 



Fig. 4. The interior of a ventral valve of this species : the sides of the valve, and a part 

 of the arching septum, have been broken away. 



Geological position and locality. The same as the preceding. 



