370 Thirty-fifth Report ok the State Museum. 



more than one-third the height of the valve below 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 stria3, somewhat fasciculate on the 

 body, and crowded and lamellose in front. 



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 the wing, with less acute 

 termination and proportionally shorter body. 



Formation and locality, in sandstones of the Chemung group at 

 Lawrenceville, Tioga county, Pa. 



Leptodesma Loxias. 

 Leptodesma Loxias, Hall. Pal. N. Y., vol. v, pt. 1 J Unpublished. 



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. 

 Eight valve unknown. Hinge-line straight, greater than the height 

 of the shell. Beak obtuse, prominent, arching over the cardinal 

 line, situated at the anterior third of the hinge. Umbonal region 

 narrow and gibbous, Subtending an acute angle. Anterior end 

 limited by a broad, nearly vertical byssal depression which extends 

 one-half the height of the valve ; margin . convex ; extremity 

 acuminate. Wing triangular, not distinctly limited, joining 

 the body near the posterior extremity^ margin oblique, nearly 

 straight, concave just beneath the hinge-line ; extremity mucronate. 



Test thin, marked by fine concentric strise, which are regular over 

 the body and wing and strongly lamellose and fasciculate on the 

 anterior end. 



A small left valve has a greatest length of 28 mm., height 17 mm., 



hinge-line 21 mm. 



• 



This species is distinguished from L. Creon and L. Demus by its 

 narrower anterior end and more rounded ventral margin. 



Formation and locality. In the Chemung group, Lawrenceville, 

 Tioga county, Pa. 



