LAMELLIBRANCHIATA. 243 



The specimens show an oblique Uiteral tooth, with obscure indications of 

 anterior teeth or folils. Ligamental area narrow, marked with fine parallel 

 striae. 



A left valve has a length of 45 mm., height 50 mm., hinge-line, when 

 entire, about 75 mm. A small right valve has a length 34 mm., height 

 27 mm., hinge-line about 45 mm. 



This species is distinguished by the great and nearly equal extent of the 

 hinge-line on both sides of the beak ; by the peculiar form of the body of the 

 shell ; and by its surface characters, which are unlike any yet observed. 



Formation and localities. In the Chemung group at Franklin, Delaware 

 county ; and a right valve referred to this species is from a point four miles 

 above Chenango Forks, Chenango county, N. Y. 



LIMOPTERA, Hall. 



LiMOPTERA PAUPERATA. 



I'LATli XXVI, FIG. 5. 



LhiinpUra pattpfmta. Hall. Prelim. Notice Lam. Shells, etc., pt. 2, p. US. Dec , lS(i9. 



Pal. N. Y., vol. V, pt. 1. Plates Hill 1 Explanations: PI. •->(), fig-. 5. J.an.. 1883. 



Shell large ; body ovate, sub-erect ; wing greatly expanded ; height much 

 greater than the length; basal margin broadly rounded; posterior side 

 gently curving from the post-basal extremity to. the beak. 



Left valve somewhat regularly convex from the umbo to the base. Ivight 

 valve unknown. 



Hinge-line straight, longer than the greatest length of the valve. 



Beak of the left valve prominent, inclined forward, rising above the 

 hinge-line, situated anterior to the middle of the liody of tlie shell. 

 Umbonal region moderately gibl)0us, abrupt ou the anterior, and more gently 

 sloping on the posterior side. 



Auricle and byssal sinus unknown. Wing large, triangular, not distinctly 

 limited from the body, and extending nearly to the post-basal extremity of 

 the shell ; margin slightly concave ; extremity abrupt (rectangular ?). 



