150 



GEOLOGT OF THE TfflRD 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 manes of the Annual Reports noticed under the head of Skaneatcles shales, Dark slaty fossilire- 

 rous shale, Compact calcareous blue shale, Olive shale, Ludlowville shale, Encrinal limestone, Moscow shale, Shales 

 near Apulia and Sherburne, and Cazenovia groups. 



(No. 8. Pennsylvania Survev,) 



38. 



No. I. Head of Dekay's dipleara (D. dekayi). No. 2. Undulated orthonaU (O. nndulata). 



No. 3. Shaip-pointed delthyris (D. mueronatos 



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 TuUy 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 



