LAMELLIBRANCHIATA. 491 



PaljEanatina sinuata, n. sp. 



PLATE 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 mm. 



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. 



