244 
PALAEONTOLOGY OF NEW YORK. 
Test marked by 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 fine concentric striae, 
which become crowded and lamellose, obscuring and partially obliterating 
the rays; the striae on the lower part of the body are conspicuous, and also 
on the wing 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. 
Limoptera cancellata. 
PLATE XXVI, FIGS. 1-4 ; and PLATE XCII, FIGS. 1-3. 
Limoptera cancellata, Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. 16. Dec., 1869. 
“ “ “ Miller, Cat. Amer. Pal. Foss., p. 193. 1877. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 26, figs. 1-4. 
Jan., 1883. 
Limoptera cancellata, var. occidens, H. and W. Twenty-Fourth An. Rep., N. Y. State Museum Nat. Hist., 
p. 199, pi. 11, figs. 12-15. 1872. 
Shell large; body sub-erect, broadly ovate; axis nearly vertical to the hinge¬ 
line ; wing expanded; height and length nearly equal; ventral margin 
very broadly 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 
