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PALAEONTOLOGY OF NEW YORK. 
Leptodesma Corydon, n. sp. 
PLATE XC, FIG. 22. 
Shell above the medium size, sub-rhomboidal; body narrowing very rapidly 
toward the beak, oblique to the hinge-line at an angle of about 30°; length 
less than twice the height; ante-byssal margin oblique, nearly straight, 
slightly impressed at the sinus, broadly curved at the base and rounded on 
the posterior extremity. 
Left valve depressed-convex below and slightly gibbous on the umbo 
(as preserved in thinly laminated shale). Right valve unknown. 
Hinge-line straight, about equal to the greatest length of the shell. 
Beak sub-anterior, directed forward, little elevated above the cardinal line. 
Umbonal region moderately gibbous, subtending an acute angle. 
Anterior end narrow, rostrate, acute, extended, defined by a distinct, 
shallow, byssal depression which produces a long, gentle curvature in the 
margin of the valve. Wing narrow, joining the body at nearly the posterior 
extremity; margin abruptly recurved below and somewhat deeply concave a 
little below the cardinal line ; extremity forming a spiniform extension. 
Test thin, marked by fine concentric striae, which are fasciculate on the 
body at unequal distances, and sharply elevated and more distinct on the 
wing. 
Interior unknown. 
A left valve of medium size has a length of 42 mm., height 25 mm., 
hinge-line about 40 mm. 
Compared with L. Clitus, the body of the shell is more elongate-ovate or 
sub-spatulate, narrowing more rapidly toward the post-extremity; the wing is 
wider and the sinuosity less deep, its greatest depth being near the cardinal 
line. 
Formation and locality. In the Chemung group, Kelly’s creek, Tioga county, 
Pa. 
