204 PALjEONTOLUGY OF NEW YORK. 



directed forward and rising; a little above the cardinal line. I'lnbonal 

 region gihbous, defined on the anterior liy the hyssal depression, ami on 

 the posterior ))y the slope of the side. 



Anterior end large, limited hx an oljlinue In ssal depression, angnlar at the 

 extremity and ronnded below. Byssal sinus extending to a point more than 

 one-third the height of the valve l)elow the beak. Wing narrow-triangular, 

 not distinctly limited: niaruin ol)li(iue, slightly convex, recurving ju.st below 

 the hinge-line ; extremity angailar. 



Test marked b\- fine, irregular stria?, somewhat fasciculate on the body, 

 and crowded and lamellose in front. 



Interior unknown. 



A well-preserved left valve has a length of 35 mm., height 20 mm., hinge- 

 line nearly 24 mm. 



The body of the valve in this species is narrower and more elongate than in 

 L. Creon, and the wing smaller ami less distinctly defined. It resemldes 

 L. Lichas, but diflers in its more gibbous undjo, stronger byssal depression, less 

 obli(|ue margin of wing, with less acute termination and ])roportionally shorter 

 body. 



Formation mid localitij. In sandstones of the Chemung group at Lawrence- 

 ville, Tioga county, Pa. 



Leptoiiesma Loxias, n. sp. 



I'l.ATK .\C. KU; U. 



Sheij. of medium size, rhomboidal : Ijody ovate, narrow above, olili(iuc to the 

 hinge-line at an angle of about 40°; Iteight one-third less than the length; 

 ante-byssal margin oblique, rounding into the sinus; ventral margin broadly 

 rounded ; posterior margin abruptly recurved. 



Left valve convex, gibbous in the middle and above. Right valve 

 unknown. 



Hinge-line straight, greater than the height of the shell. 



Beak obtuse, prominent, arching over the cardinal line, situated at the 



