LAMELLIBRANCHIATA. 505 



Formation and locality. In the shales of the Hamilton group, near Jefferson, 

 Schoharie county, N. Y. 



Elymella patula, n. sp. 



PLATE XL, FIG. 11. 



In part Modiomorphaf hyalea. Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 40, tigs. 



5-H. 1883. 

 Not " " " Prelim. Notice Lamellibranchiata, 2, p. 79. 1870. 



Shell below the medium size, obliquely sub-ovate, broader anteriorly; length 

 one-third greater than the height; basal margin gently curved, abruptly 

 recurving into the anterior and posterior extremities ; posterior margin 

 abruptly rounded, more gently recurving to the hinge-line ; cardinal margin 

 nearly straight for about half the length of the shell, then gently curving 

 toward the posterior end. Anterior end regularly rounded, short, abruptly 

 curving into the lunule, not limited by any sinus or depression. 



Valves depressed-convex in the posterior and lower portion, and more con- 

 vex in the umbonal region. 



Hinge-line straight, about one-half the length of the shell. 



Beaks small, sub-anterior, distinct, incurved. Umbonal region moderately 

 convex, not defined nor continued as a ridge on the posterior slope. 



Test thin, marked by fine, sharp, elevated concentric striae, which are 

 sometimes aggregated into fascicles, giving the surface an undulated charac- 

 ter. Interior unknown. 



The specimen has a length of 32 ram. and a height of 20 mm. 



This species resembles E. nuculoides, but differs in the slightly longer and 

 wider anterior end, less gibbous valves and less prominent umbo ; the posterior 

 end is also more narrowed toward the extremity. 



Formation and locality. In the shales of the Waverly group, at Medina, 0. 



