18 
GEOLOGY OF THE FOURTH DISTRICT. 
III. NEW-YORK SYSTEM. 
This includes all the products between the Taconic and the Old Red Systems, commencing with the 
lowest known sedimentary rock, and terminating at the base of the latter. 
Under the New-York System are included the following rocks and groups, in their order of succes¬ 
sion : 
NEW-YORK 
SYSTEM. 
Geographical subdivisions. 
Champlain Division. 
Ontario Division, .. 
Helderbf.rg Series. 
Erie Division, 
Systematic subdivisions, founded upon the fossil and lithological 
characters. 
1. Potsdam sandstone. 
2. Calciferous sandrock. 
3. Black-river limestone group, embracing the Chazy 
and Birdseye. 
4. Trenton limestone. 
5. Utica slate. 
6. Hudson-river group. 
7. Grey sandstone. 
8. Oneida or Shawangunk conglomerate. 
9. Medina sandstone. 
< 10. Clinton group. 
11. Niagara group, including shale and limestone. 
' 12. Onondaga-salt group. 
13. Water-lime group. 
14. Pentamerus limestone. 
15. Delthyris shaly limestone. 
16. Encrinal limestone. 
17. Upper Pentamerus limestone. 
18. Oriskany sandstone. 
19. Cauda-galli grit. 
20. Schoharie grit. 
21. Onondaga limestone. 
22. Corniferous limestone. 
'23. Marcellus slate. 
C Moscow shales. 
24. Hamilton group. < Encrinal limestone. 
( Ludlowville shales. 
, 25. Tully limestone. 
1 26. Genesee slate. 
C Portage sandstone. 
27. Portage or Nunda group. < Gardeau flagstones. 
£ Cashaqua shale. 
28. Chemung group. 
