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PALEONTOLOGY OF NEW YORK. 
tion, becoming straight toward the posterior. Posterior extremity abruptly 
acute, not attenuate. Cardinal line straight, oblique. Anterior end large, 
broadly rounded, comprising half the shell. 
Yalves convex, very gibbous in the anterior portion and in the umbonal 
region. 
Beaks behind the anterior third, prominent, rising above the hinge-line. 
Umbonal ridge defined, angular, curving downward, abruptly sloping to the 
posterior extremity. 
Surface marked by fine, even, concentric striae, which are obsolete on the 
post-cardinal slope. Interior unknown. 
Two specimens measure respectively 9 and 11 mm. in length, and 6 and 7 
mm. in height. 
This species differs from L. rostellata in the shorter and less curved posterior 
end; the anterior portion is broader and more extended; the beaks are more 
distant from the anterior extremity. 
Formation and localities. In the shaly sandstones of the Hamilton group, from 
near Summit and Jefferson, Schoharie county, N. Y. 
Leda rostellata. 
PLATE XL VII, FIGS. 42-47. 
Nuculites rostellata, Conrad. Geol. Sui'v. N. Y., Ann. Rep., p. 50. 1841. 
Leda? rostellata (Conrad), Hall. Prelim. Notice Lamellibranchiata, 2, p. 5. 1870. 
Leda (Nuczdaua) rostellata (Conrad), Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 47, 
figs. 45-47. 1888. 
“ “ 'perstriata, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 47, figs. 
42-44. 1883. 
Shell small, falciform; length more than twice the height; basal margin 
gently curving from the posterior extremity, more rapidly curving anteriorly. 
Posterior end attenuate, arching upward, with the extremity narrowly 
rounded or sub-truncate. Cardinal line oblique, declining posteriorly, and 
regularly curved. Anterior end comparatively short, abruptly rounded. 
Valves convex, somewhat gibbous in the umbonal region, depressed-convex 
posteriorly. 
