LOWER HELDERBERG ROCKS. 267 



CjTuicardinia dorsata ( n. s.)- 



Plate XLIX A. Fig. 2. 



Shell transversely elongated, scarcely gibbous : umbones depsessed ; 



anterior extremity rounded ; posterior extremity obliquely subtruncate ; 



the cardinal margin compressed, with an obtuse oblique ridge separating 



it from the body of the shell. 

 Surface marked by concentric ridges, which are more conspicuous on 



the anterior part of the shell, becoming obsolete on the middle and 



posterior portions ( perhaps from maceration and wearing before the 



shell was imbedded). 



The only specimen observed is in a shaiy limestonej and is not well preserved. 

 It differs, however, conspicuously from any other species seen in this group. 



Fig. 2. The right valve of this species. 



Geological position and locality. In the shaly limestone near the upper part of 

 the Lower Helderberg group : Near Hudson, Columbia county. 



Cypricardinia sublamellosa ( n. s.). 



Plate L. Fig. 1. 



Shell transversely elongated ; anterior extremity contracted ; umbones 

 very depressed ; posterior slope convex, without a defined ridge ; ex- 

 tremity somewhat acutely rounded. 



Surface marked by rounded concentric striaB or ridges, whicli are more 

 prominent on the posterior half of the shell. 



A single specimen only has been observed. 



Fig. 1. The right valve, natural size. 



Geological position and locality. In the compact calcareous layers of the middle 

 portion of the Lower Helderberg group : Helderberg mountains, Albany county. 



