LAMELLIBRANCHIATA. 393 



hinge-line ; and from E. depressa in its more gibbous form, narrower posterior 

 end, and more regular curvature of the basal margin into the posterior margin. 

 Formation and locality. In the Burlington sandstones, at Burlington, la. 



EdMONDIA ? TENDISTRIATA, n. sp. 



PLATE LXIII, FIGS. 9, 10 ; AND PLATE XCV, FIG. 17. 



Cardvnnorpha xuborbiculariJi, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 63, figs. 9, 10. 



1883. 

 Not " " " 8. A. Miller. Cat. Am. Pal. Foss., p. 186. 1877. 



Not UngiUina suix>ti)icidarig. Hall. Geol. Surv. N. Y., Rep. Fourth Dist., p. 243, t. 106, fig. 2. 1843. 



Shell of medium size, sub-orbicular ; length a little greater than the height. 

 Pallial margin regularly curved. Cardinal line short and straight. 



Valves moderately convex, scarcely gibbous in the umbonal region. 



Beaks sub-central, slightly tumid, rising but little above the hinge-line. 

 Umbonal slope undefined. 



Surface marked by fine, regular, concentric striae, which are cancellated by 

 fine radiating striae ; the latter more conspicuous on the posterior slope. 

 Interior unknown. 



The specimen described has a length of about 25 mm. and a height of 23 

 mm. 



This species has been compared with and supposed to be identical with Ungu- 

 lina suborbicularis, loc. cit., but it is entirely distinct from that form and from a 

 different horizon. Its generic relations cannot be satisfactorily determined, and 

 it is placed provisionally under the genus Edmondia. But two specimens have 

 been observed and are worthy of note on account of their peculiar form and 

 surface characters. 



Formation and locality. In the shales of the Chemung group, near Elmira, 

 N. Y. 



