\-2-2 PALEONTOLOGY OF NEW YORK. 



I. .ft valve gibbous above, gently convex below. Right valve unknown. 



Hinge-line straight, about equal to the beight of the valve. 



Beak at about the anterior third of the binge, directed forward, prominent, 

 rising above the cardinal line. Umbonal region gibbous, nearly rectangular. 



Ear rounded, defined by a distinct byssal depression whicb extends 

 forward from the beak. Wing small, joining the body near the posterior 

 extremity, not strongly defined ; margin gently concave ; extremity produced. 



Test marked by fine concentric stride, and undulating or interrupted 

 filiform radiations, with wider interspaces, which have probably been marked 

 by liner intermediate striae. The concentric lines are obscure in the cast 

 and appear as a few irregular concentric undulations. 



Interior unknown. 



The specimen is 23 mm. in length, 15 mm. in height, hinge-line 10 mm. 



Formation and locality. In the lower part of the Chemung group at Ithaca, 

 N. Y. 



ACTINOPTERIA EPSILON. 

 PLATE XXIII, FIGS. 4, 8, (5 and 8?). 



.1. tinopti riu epsikm, Hall. Pal. N. V., vol. v, pt. 1. Plates and Explanations: PI. -3. figs. A. 8. .Ian., 1883. 



Shell of medium size, rhomboidal ; body ovate, oblique to the axis at an angle 

 of about till ; height about three-fourths the length ; anterior margin rounded 

 into a very abrupt sinus; base broadly curved; post-basal side abruptly 

 rounded. 



Left valve moderately convex. Right valve depressed-convex above, Hat 

 or concave below. 



Hinge-line straight, length somewhat less than the height of the valve. 



Beaks anterior, acute in the left valve; prominent and elevated above the 

 binge. Umbona] region gibbous, subtending an angle of less than 60°. 



Ear short, defined by a deep, abrupt byssal depression. Wing triangular, 

 joining the body below the middle, not strongly defined; margin regularly 

 concave ; extremity acute and produced. 



