150 
GEOLOGY OF THE THIRD DISTRICT. 
These shales may be traced continuously from the east to the west end of the district; the 
line of continuity being only broken by the valleys, through which the many creeks and brooks 
flow at right angles to its direction, or line of northern outcrop ; the points noticed in the report 
being such only as appeared to be the most prominent or important. 
22. HAMILTON GROUP. 
It embraces all the masses of the Annual Reports noticed under the head of Skancateles shales, Dark slaty fossilife- 
rous shale, Compact calcareous blue shale, Olive shale, Ludlowville shale, Encrinal limestone, Moscow shale, Shale? 
near Apulia and Sherburne, and Cazenovia groups. 
(No. 8. Pennsylvania Survey.) 
36. 
£ 
No. 1. Head of Dekay’s dipleura (D. dekayi). No. 2. Undulated orthonata (Q. undulata). 
No. 3. Sharp-pointed delthyris (D. mucronatus 
This group takes its name from the town of Hamilton in Madison county, which contains 
no other rock, and where the best opportunity exists of examining some of the important 
members of which it is composed, and where its fossils are in great abundance. To many 
the name is acceptable, as it perpetuates the counsellor of the right hand of Washington. 
The Hamilton group, for the present, includes all the masses between the upper shales of 
Marcellus, and the Tully limestone. That it may be divided to advantage, admits of little 
doubt, as might be supposed from the annual reports, and from its thickness; but up to the 
present time, no advantageous or satisfactory division has been suggested, except for the west 
