488 
PALAEONTOLOGY OF NEW-YORK. 
Caiimrium elongatum (n.s.). 
Plate XCY A. Fig. 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 differs from C. t.ypum 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. 
