LAMELLIBRANCHIA TA . 
491 
Pal^eanatina sinuata, n. sp. 
FLATE XCVI, FIG. 4 . 
Shell small, obovate, length about twice the height; basal margin gently 
curving, straight in the middle. Posterior extremity rounded below and 
truncate above. Cardinal line gently arcuate. Anterior end narrow, 
rounded. 
Left valve depressed-convex below, becoming gibbous in the umbonal 
region. Right valve unknown. 
Beaks at about the anterior fourth, low, scarcely rising above the hinge¬ 
line. The valve, from the beak downward, is depressed, but without a 
distinct cincture. Umbonal slope prominent, obtusely sub-angular, limited 
above by a distinct groove or sinus extending to the post-inferior extremity. 
Cardinal slope convex, limited below by the sinus bordering the umbonal 
ridge. The cast of the interior preserves the remains of fine concentric 
striae, which were abruptly sinuate in passing over the umbonal ridge and 
sinus. 
A specimen has a length of 21 mm. and a height of about 12 mni. 
This species is shorter and broader than any of the preceding, and is readily 
distinguished by the defined umbonal ridge, with the narrow sinus on the 
upper side. 
Formation and locality. In the Chemung group, at Warren, Pa. 
