L74 PALEONTOLOGY OF NEW YORK. 



This species differs from L. Chemungensis in its more erect form, and the ear 

 is without the strong fold and marked sulcus of that species; the wing is also 

 less extended and the margin less concave. 



Formation and locality. In the Chemung group in the valley of Cayuta creek, 

 Broome county, N. Y. 



Leiopteru Torrevi, n. sp. 



PLATE XXn, FIGS 6,7; VND PLATE LXXXVIU, FIG. H. 



Shell of medium size, rhomboidal, sub-falcate; body narrow-ovate, arcuate. 

 oblique at an angle of less than 45° with the hinge: height equal to about 

 two-thirds of the length ; anterior and basal margins broadly curving from 

 the byssal sinus: post-basal margin produced and abruptly recurved. 



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

 unknown. 



Hinge-line straight, about equal to the height of the valve. 



Beak sub-anterior, directed forward, acute, prominent and arching over 

 the hinge. Umbonal region narrow, ventricose, well-defined, subtending an 

 acute angle. 



Ear large, bending downward, marked by a strong oblique fold, limited by 

 a broad, vertical byssal depression and shallow sinus: margin convex; 

 extremity apparently obtuse. Wing joining the body above the posterior 

 extremity, limited by the nearly vertical post-umbonal slope, which makes a 

 more or less marked sulcus: margin concave : extremity produced, acute. 



Surface marked by fine striae of growth which are somewhat regularly 

 lamello.se on the body of the valve. 



A left valve has a length of .!'.• mm., height '2'2 mm., hinge-line 1^1 mm. 



This species differs from /,. CItemimgensis in its proportionally greater length, 

 narrower umbo, more convex and oblique left valve, and shorter wing. 



Formation and local it;/. In a sandstone and conglomerate of the Chemung 

 group near Panama, X. V. 



