OF DENISON UNIVERSITY. 
49 
incurved into the cavity below the deltidial plites. Surface concen- 
trically striate with crowded larnelliform ridges toward the sides and 
front.” 
Length of our largest specimens nearly 30 mm, width 27 mm. 
Varying greatly in form and size. The casts figured on Plate V give 
a good idea of the vascular markings. 
Freestone of middle Waverly. Typical specimens are from the 
Chemung of New York. 
Centronella julia, Win. 
(Plate II, Fig. 5.) 
Shell small, lenticular, ovate or somewhat transverse in outline ; 
valve moderately convex, its beak covered by the higher, incurved 
beak of the more convex ventral valve ; area absent. Surface marked 
by concentric lines of growth and radiating lines (impressed from the 
interior upon the cast?) Internal characters of the genus. 
Many specimens of this species may be found in the freestone 
overlying shales above congl. II, at Newark and eastward. It agrees 
in external feature perfectly with Prof. Hall’s figures of this species. 
Other forms are ifiustrated in figures 4 and 8 of Plate II, and may be 
refered to this genus. As, however, we know nothing of the essen- 
tial characters we may forbear burdening synonomy with meaningless 
names. 
Athyris ohioensis, Wm. 
(Plate II, Fig. i.) ^ 
Some doubt attends the identification, on account of the condition 
of our specimens, but Prof. Winchell was good enough to compare 
our casts with the types and considers the identification as a proba- 
ble one. 
Athyj'is lamellosa, Level l. i 
(Plate II, Fig. 7.) 
The specimens figured are from the layer below congl. I, and we 
