lillS PALEONTOLOGY OF NEW YORK. 



Left valve moderately convex below, gibbous on the umbo. Right valve 

 ilai below, depressed-convex in the middle, ami more convex above, propor- 

 tionally wilier than the left, ami distinguished by its depressed-convex form. 



Hinge-line straight : Length greater than the Length of the valve. 



Beak of left valve Bub-anterior, acute, directed forward, rising slightlv 

 above the binge-line. Beak of right valve depressed, not rising above the 

 cardinal line. Umbonal region of left valve moderately gibbous, subtending 

 a \cr\ acute angle. 



Anterior end greatly extended, acute, rostrate, limited by a shallow hvs.-al 

 depression. Wing narrow-triangular, joining the body at the posterior 

 extremity, defined by tlie recurving of the stria?; margin abruptly and 

 symmetrically concave: extremity produced beyond the posterior limit of 

 the shell. 



Test thin, marked by fine, sharp, closely arranged, concentric striae; which 

 are sometimes fasciculate upon the body and anterior side, and very distinct 

 upon the wing. Partial casts of the interior of the left valve give indications 

 of fine radii which appear to belong to the intimate structure of the shell. 



Characters of the interior unknown. 



A left valve has a length of 32 mm., height 16 mm., and hinge-line 

 37 mm. A right valve has a length of 34 mm., height 1'.' mm., and hinge- 

 line 4(1 mm. 



This species is distinguished by the great length of the hinge-line, its narrow 

 outline, and anterior extension. It approaches Pteronites in character, hut 

 differs in having a distinct wing, more depressed form, and a recurvation of 

 the stria- along the post-umbonal slope. 



Formation and localities. In the Chemung group, Philipsburg, Alleghany' 

 county. N. V.. and Kelly's creek. Tioga county, Pa. 



