160 PALAEONTOLOGY OF NEW YORK. 



This species boars some general resemblance in form to Adinopteria decussata 

 and A. Boydi, but is distinguished by the absence of rays. It differs from 

 L. Greeni, fig. 9, pi. xx, in its more oblique form and greater proportional length. 



Formation and localities. In shales of the Hamilton group, on the shore of 

 Canandaigua lake, and ;it Bellona, Yates county, N. Y. 



Leiopteria Greeni. 



PLATE XX, PIGS. 9, 13; and PLATE I.XXXV1II, FIGS. SSI, 22. 

 Leiopteria Greeni, Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. 20, figs. 9, 12. Jan., 1883. 



Shell large, sub-rhomboidal ; body moderately oblique, broadly ovate ; length 

 a little greater than the height; margins regularly rounded, somewhat 

 extended posteriorly. 



Valves moderately and nearly equally convex; similar in character. 



Hinge-line straight, equalling or greater than the length of the shell. 



Beaks acute, anterior, inclined forward, arching over the hinge in the 

 left valve ; less prominent in the right. 



Ear short, limited by a sulcus and sinus which is deeper in the right valve. 

 Wing large, triangular, denned only by the abrupt bending of the striae ; 

 margin concave ; extremity acute. 



Test thin, marked by numerous, closely arranged, concentric lines of 

 growth, and, at somewhat regular intervals, by sharp, projecting lamellose 

 stride ; and corresponding with these, are regular concentric undulations, 

 which are shown strongly on the cast, and but partially seen on the exterior 

 surface. The striae mark the wing in the same manner as the body, and are 

 crowded on the ear. 



Ligamental area narrow, marked by a single groove. 



A large specimen measures 57 mm. in length, 51 mm. in height, hinge- 

 line 58 mm. 



This species resembles L. Conradi, but is broader, with comparatively greater 

 height, less obliquity, and less extended posterior wing. 



Formation and localities. In the shales of the Hamilton group at Bellona, 

 Fates county, and on the shores of Cayuga and Canandaigua lakes, N. Y. 



