OF DENISON UNIVERSITY 
6 
obliquely ovate, length considerably exceeding the height ; post basal 
side considerably extended ; ear straight, almost acute, anterior side 
obliquely truncate; body making an angle of about 45°, with the 
hinge line. Left valve shortest, most gibbous ; beak one fourth from 
anterior, rather prominent, but not incurved, ear rather convex, with 
a broad shallow byssal sinus, wing large flat, the posterior margin 
meeting the hinge at an angle of about 90° or more, acute at the very 
angle only. The hinge margin is greatly thichened. The difference 
between the two valves is slight, the beak of the right being generally 
in advance of the other, and the front margin is more uniformly curved. 
Entire length of hinge linge 22 mm, height 14 mm, length from 
beak to antero-ventral angle 19 mm. Surface marked by concentric 
lines. This species somewhat resembles L. rafinesquii, H , but differs 
in being more oblique and longer, with straighter and longer hinge and 
less produced beak and straighter posterior margin. Leptodesma hec- 
tor is somewhat more like our species, but exhibits an opposite extreme. 
This species is characteristic of a zone several feet thick, about 40 feet 
below conglomerate I, in connection with other fossils of a more or 
less Devonian habit. This species may be compared with L. torreyi, 
but is not so produced; it also resembles Leptodesma nereus. Compare 
also L. naviforme. 
Leiopteria Jialli, sp. n. 
(Plates VII, Fig. 31, Cf. Fig. 32.) 
\ 
Shell of moderate size; sub-rhomboidal ; body narrowed above, 
obliquely ovate; height greater than length at hinge; margin strongly 
sinuous; ears rounded, somewhat depressed, short; wings broad, ex- 
tended, acute ; hinge-line straight. Valves nearly similar, left valve 
rather more convex. Right valve moderately convex; body diverging 
from hinge-line at an angle of about 45° ; wing acute ; posterior mar- 
gin strongly concave, postero- ventral extremity rather sharply curved ; 
anterior margin abruptly flexed near the middle, anterior to which it is 
gently concave; ear rounded, depressed. Left valve with smaller 
wing more convex, especially ventrally. Surface of both valves 
marked by conspicuous concentric folds. Hinge with a decided 
groove and thickened ridge. Beak of right valve high, but not pro- 
jecting dorsally, that of the left valve extending beyond hinge-line. 
