162 PALEONTOLOGY OF NEW YORK. 



sions: length 39, 34, and 25 mm., height 41, 38, and 26 mm., hinge-line 37, 

 39, and 26 mm. The right valve, mentioned above, is 23 nun. in length. 25 

 nun. in height, and 23 mm. along the hinge-line. 



This species resembles the two preceding, but the form of hody is more 

 narrowly ovate, the obliquity appears to he intermediate between the two; 

 the ear is less strongly defined ; the wing is comparatively narrower, and less 

 extended at the extremity. 



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

 at Skaneateles lake: at Bellona, Yates county, and Leonardsville, Madison 

 county, X. Y. : a single specimen from the Corniferous limestone of Delaware. 

 Ohio, has been referred to this species. 



Leiopteria Sayi, n. sp. 



PLATE I.XXXV11I, FIGS. 16-20. 



Shell above the medium size, sub-orbicular; hody very broadly ovate, scarcely 

 oblique; height greater than the length: margin nearly straight in front, 

 thence regularly rounded. 



Left valve very convex, gibbous in the umbonal region. Right valve 

 smaller and less convex. 



Hinge-line straight, longer than the length of the shell. 



Beaks acute, situated near the anterior extremity of the hinge, prominent, 

 inclined forward, arching over the hinge-line. I'mhonal region ample, sub- 

 tending a right angle. 



Ear small, bending downward, defined by a broad, shallow sulcus. Byssal 

 sinus narrow. Wing large, triangular, greatly extended along the hinge-line, 

 defined by the retral bending of the stria': margin concave: extremity acute. 

 The wing of the right valve is very broad, tlat. and much extended: not dis- 

 tinctly defined. 



Surface marked by line, closely arranged stria' of growth, with distant. 

 elevated lamelhe. which are extensions of strong fascicles of stria'. These 

 leave angular concentric folds and undulations in the casts. The stria' are 



