FOSSILS OF THE LOWER SILURIAN. 67 
of the great vertical difference in the geologic horizon at which the two 
forms occur, render the probability of a specific identity very doubtful. 
Formation and localities. Upper portion of the Pogonip Group, White 
Mountain and Goodwin Canton, Eureka District, Nevada. Also in the col- 
lection of the School of Mines, Columbia College, New York, collected by 
Dr. J. 8. Newberry in the Pahranagat Range, Nevada. 
Receptaculites ellipticus, n. sp. 
Plate xi, fig. 12. 
This is an elongate, flattened, curved form, with a strongly elliptical 
transverse section, the curvature being with the major diameter of the 
section. The central depression is deep, but not as large proportionally as 
in R. elongatus. The plates of the ectorhin are of medium size, 1.75™™ by 
1.25™, and arranged as in the preceding species. The cylindrical tubes 
uniting the ectorhin and endorhin are strong and appear to be round and 
smooth, except where marked by the constriction and connecting basal 
stolons. The plates of the endorhin are concealed by the adhering matrix 
in all the examples in the collection. 
The illustration shows the curvature and general form of a well-marked 
example of the species. It is specifically distinct from any described form 
that we know of, although allied to Receptaculites infundibulus Hall (Rep. 
Geol. Surv. Wisconsin, 8vo, pam., p- 16, 1861) = Ischadites tessellatus Win- 
chell and Marcy, of the Niagara Group of Illinois (Mem. Bos. Soc. Nat. Hist., 
vol. i, p. 85, pl. ii, fig. 3, 1865), from which it differs in the size of the 
ectorhinal plates and other details of structure. 
Formation and localities—Upper portion of the Pogonip Group, White 
Mountain, Goodwin Canon, and Fish Creek Mountains, Eureka District, 
Nevada. 
BRACHIOPODA. 
Genus OBOLELLA Billings, 
Obolella ? ambigua, n. sp. 
Plate i, fig. 2a, b, ©. 
Shell of medium size for the genus as now known, ovate, moderately 
convex; surface lamellose; shell caleareous. Ventral valve ovate, broadly 
