16*2 
PALAEONTOLOGY OF NEW-YORK. 
Discina vaiiuxeini (n. s.). 
Plate YIII. Fig. 1 a, b. 
Shell orbicular or broadly subelliptical. Dorsal valve very convex : apex 
excentric, and pointed towards the posterior extremity of the shell. 
Surface marked by tine closely arranged concentric striae and finer 
radiating striae, exhibiting a finely cancellated appearance under a 
magnifier. Inferior valve unknown. 
This species differs but little in form from D. discus. The dorsal valve is much 
more convex, the beak somewhat acute, and the concentric striae more closely 
arranged. 
A single individual only of the dorsal valve has been found, and I am unable 
therefore to speak of the variety it may exhibit when studied with more specimens. 
Fig. 1. Profile view. 
Fig. 1 a. Dorsal view, showing the form of the shell. 
Fig. 1 b. Enlargement of surface, showing the radiating and concentric striae ( the latter 
are not strong enough in proportion to the others). 
Geological jwsition and locality. In the upper part of the Waterlime group : 
Quarry northwest of Manlius-square. 
Orthis oblata (n. s.). 
Plate X. Fig. 1 - 22. 
Compare Orthis hybrida, Murchison, Sil. System, p. 63, pi. 13, f. 11; also Pal. N.Y. Vol. ii. 
“ Orthis orbicularis, Sowerbv. 
“ Orthis vanuxemi of the Hamilton group, N.Y. 
Shell in the young state longitudinally subovate, and varying from 
circular to transversely oval in its stages of growth, resupinate. Ven¬ 
tral valve convex at the beak, flattened in the middle, and concave 
towards the front. Dorsal valve very convex in the middle and towards 
the beak : beaks of the two valves nearly equally elevated; that of 
the ventral valve pointed : area very small : foramen large. 
Surface finely striated : stride frequently bifurcating and curving towards 
the lateral and cardinal margins, concentrically marked by finer striae 
