LAMELLIBRANCHIATA. 271 



MODIOMOBPHA PUTILLUS. 



PLATE XLI, FIGS. 1, 2. 



ModUniwrpha putillus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 41, figs. 1, 2. 18S3. 



Shell small, sub-ovate, gibbous; height more than half the length; anterior 

 margin abruptly rounded ; base broadly curving. Anterior end convex, lim- 

 ited by a broad depression extending backward from a point just anterior 

 to the beak to the ventral margin. 



Valves very convex and obtusely sub-angular along the post-umbonal 

 slope; the point of greatest convexity is a little anterior to the middle of 

 the length of the shell. 



Hinge-line slightly oblique, somewhat longer than the height of the shell. 



Beaks prominent, curving down to the hinge-line. Umbonal region 

 gibbous. 



Test not preserved. The internal mould shows traces of strong concentric 

 laminae which probably marked the exterior shell. 



Anterior muscular impression comparatively large, situated close to the 

 anterior margin. Pallial line strongly impressed. Other characters of the 

 interior unknown. 



A specimen of normal form and preserving both valves has a length of 17 

 mm., height 10.5 mm., and depth of both valves 9 mm. 



This species more nearly resembles M. neglecta of the Chemung group than 

 any other, but may be distinguished by its narrower form and less oblique 

 hinge-line. 



Formation and locality. In the Schoharie grit, Schoharie, N. Y. 



MODIOMORPHA (?) PONDEROSA. 



PLATE XXXIV, FIGS. 11, 12 ; ANO PLATE XXXV, FIG. 8. 



JSkmffulnolUett ponderomis, Kkhh. Prelim. Notice Lamellibranchiata, 2, p. 35. 1870. 

 MoMomorpha ponderosa, Hall. S. A. Miller, Cat. Ainer. Pal. Foss., p. 196. 1877. 



" " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 34, figs. 11, 12. 



1883. 



Shell large, rhomboid-ovate, gibbous ; length one-third greater than the height; 

 posterior margin broadly rounded; basal margin slightly concave toward 



