122 
PALEONTOLOGY OF NEW YORK. 
Left valve gibbous above, gently convex below. Right valve unknown. 
Hinge-line straight, about equal to the height of the valve. 
Beak at about the anterior third of the hinge, directed forward, prominent, 
rising above the cardinal line. Umbonal region gibbous, nearly rectangular. 
Ear rounded, defined by a distinct byssal depression which 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 striae, and undulating or interrupted 
filiform radiations, with wider interspaces, which have probably been marked 
by finer 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 16 mm. 
Formation and locality. In the lower part of the Chemung group at Ithaca, 
N. Y. 
Actinopteria epsilon. 
PLATE XXIII, FIGS, i, 8, (5 and 6?). 
Actinopteria epsilon, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PL 23, tigs. 4, 8. Jan., 1883. 
Shell of medium size, rhomboidal; body ovate, oblique to the axis at an angle 
of about 60°; 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, flat 
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 
hinge. Umbonal 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. 
