244 PALEONTOLOGY OF NEW YORK. 



Tesl marked b\ strong rounded radii, with alternate smaller ones ; or finer 

 bifurcating rays between, which are somewhat curved as they approach the 

 beak. The entire surface of the shell is marked by line concentric striae, 

 which become crowded and lamellose, obscuring and partially obliterating 



the rays: the striae Oil the lower part of the body are conspicuous, and also 

 mi the win»- and especially toward the hinge-margin. In the cast the rays 

 show a somewhat nodose character which is probably due to the unequal 

 weathering of the concentric lamellae. 



Interior characters and ligamental area unknown. 



The specimen described has an approximate height of 75 mm., and a 

 length of 65 mm. (The figure is incorrect in its proportions.) 



This species differs from L. macroptera, and from L. cancellata, in its lesser 

 gibbosity and its much stronger radii. A single, ill-preserved, specimen from 

 the Hamilton group, possesses characters similar to this species, but the iden- 

 tity of the two cannot be positively determined without more material. 



Formation and locality. In the higher beds of the Upper Helderberg lime- 

 stone at Stafford, Genesee county, N. Y. 



LlMOPTERA CANCELLATA. 

 PI. ATI-: XXVI. FIGS. 1-4 ; am. PLATE X( II. FIGS. 1 3. 



lAmoptera cancellata, Halt,. Prelim. Notice Lam. Shells, etc., pt. 2, p. 16. Dec., 1869. 

 " Miller, Cat. Amer. Pal. Foss., p. 193. 1877. 



Pal. N. V.. vol. v, pt. 1. Plates and Explanations: PI. 26, figs. 1-4. 

 Jan., 1883. 

 Limoplera cancellata, ear, occi lens, 11. \m> W. Twenty-Fourth An. Rep., N. V. State Museum Nat. Hist., 



p. 199, pi. 11, figs. 12-15. 1872. 



Shei i. Large ; body sub-erect, broadly ovate; axis nearly vertical to the hinge- 

 line: wing expanded: height and length nearly equal; ventral margin 

 ver\ 1 in >-m 1 1 \ rounded ; anterior margin expanded below and contracted 

 above; post-basal side expanded, recurving somewhat abruptly and extending 

 in a sub-arcuate line to the beak. 



Valves very unequal. Left valve moderately convex below, gradually 



