14S 
GEOLOGY OF THE THIRD DISTRICT. 
List of Fossils from the Reports, etc. of T. A. Conrad, identified and named up to thu 
period, which are found in the Corniferous limestone. 
Testacea, or Shells. 
Delthyris acuminata. Platyceras dumosum, formerly Pileopsis tubifer 
Strophomena undulosa. Cyrtoceras trivolvis. 
— rugosa. — matheri. 
Crustacea. 
Odontocephalus selenurus 
21. MARCELLUS SHALES. 
Commencement of the Pyritiferous Rock (or Third Greywacke) of Eaton. 
Two divisions —Lower, calcareous, fossiliferous and somewhat fissile; the upper, shaly, breaking into 
small irregular fragments. 
Color black, usually dark brown when altered. It is the first mass which rises upon the top of the Helderberg series of 
limestone, and is coextensive with it. It greatly resembles the Utica slate in mineral character, and could readily 
be confounded with it. 
35. 
No. 1. Expanded goniatite (G. expansus), natural size ; the segment above represents the back of the chambers, which differ 
from No; 2. 
2. Segment of the Marcellus goniatite (G. marcellensis), reduced about one half in size. 
3. Limitary orthis (O. limitaris). 
4. Marcellus cypricardites (G. marcellensis). 
These shales extend east and west through the district, commencing near the Hudson, and 
ending on Lake Erie. They are conveniently divided into two masses, from the presence 
of limestone and fossils in the one, and their absence generally in the other. The limestone 
is very impure, of the same dark color of the shale, rarely forming continuous layers or beds, 
