Jul PALJEOSTOUKSY OF NEW YORK. 



directed forward and rising a Little above the cardinal line. Umbonal 

 region gibbous, defined on the anterior by the byssal depression, and on 

 the posterior by the slope of the side. 



Anterior end large, limited by an oblique byssal depression, angular at the 

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

 one-third the height of the valve bekrw the beak. Wing narrow-triangular, 

 not distinctly limited; margin oblique, slightly convex, recurving just below 

 the hinge-line; extremity angular. 



Test marked by fine, irregular striae, 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 and less distinctly defined. It resembles 

 L. Lichas, but differs in its more gibbous umbo, stronger byssal depression. Less 

 oblique margin of wing, with less acute termination and proportionally shorter 

 body. 



Formation and locality. Ln sandstones of the Chemung group at Lawrence- 

 ville. Tioga county. Pa. 



Leptodesma Loxias, n. sp. 



PLATE XC. FIG. II. 



Shell of medium size, rhomboidal : body ovate, narrow above, oblique to the 

 hinge-line at an angle of about 40°; height 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 

 unknow n. 



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



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



