EQUIVALENTS OF AMERICAN STRATA. 
519 
Tabular arraugment of lower American strata, showing the equivalency of those known by 
different names in the several States. 
New-Yobk Survey. 
1. Potsdam sandstone. 
2. Calcifcrous tandrock. 
*3. Black-river and Birdseye lime¬ 
stone. 
*4. Trenton limestone. 
5. Utica slate. 
G. Hudson-river group. 
7. Oneida conglomerate. 
8. Grey sandstone. 
9. Medina sandstone. 
10. Clinton group. 
11. Niagara group. 
12. Onondaga salt group. 
13. Water limestone. 
14. Pentamerus limestone. 
15. Delthyris shaly limestone. 
lG. Encrinal limestone. 
17. Upper Pentamerus limestone. 
18. Oriskany sandstone. 
19. Cauda-galli grit. 
20. Schoharie grit. 
21. Onondaga limestone. 
22. Corniferous limestone. 
23. Marcellus shale. 
24. Hamilton group. 
25. Tully limestone. 
26. Genesee slate. 
27. Portage group. 
28. Chemung group. 
Pennsylvania and 
Virginia Surveys. 
No. 1. 
No. 2. 
No. 2. 
No. 2. 
No. 3. 
No. 3. 
No. 4. 
No. 4. 
No. 5. 
No. 5. 
Part of No. 6. 
! Included in No. G. 
[ if existing. 
No. 7. 
No. 7. 
No. 8. 
No. 8. 
No. 81 
No. 9. 
Ohio Survey. 
Wanting. 
Wanting. 
[Blue limestone and marl 
[ formation. 
Wanting. 
Wanting. 
Wanting. 
Part of Cliff limestone. 
f This formation is but par 
tially developed in the 
! southwest part of the 
State, but more exten¬ 
sively in the northern 
part. 
Wanting, or not recog¬ 
nized in the western 
States. 
Upper part of the Cliff 
$ limestone. 
Black slate. 
( Wanting, or but partially 
\ developed. 
Wanting. 
Wanting It 
( Waverly sandstone 
( series. 
Michigan Survey. 
f Mackinac limestone; grey, 
1 sandy and porous lirne- 
/ stone. 
In this series are included 
the Little Traverse bay 
limestone, Black bitu¬ 
minous limestone, Blue 
j limestone in thick regu¬ 
lar layers. Thunder 
^ bay limestone 1 
^ Corniferous limestone. 
f Shales. Black aluminous 
( shale. 
fSoft, light colored sand¬ 
stones. Argillaceous 
j slates and flagstones of 
] Lake Huron. Sand- 
| stones of Point Aux 
Barques. 
The State of New-York presents a better opportunity for defining the limits of the several 
subdivisions of the system, than any point yet observed to the west and south. The different 
members are more numerous, but at the same time they are usually well marked, either 
by lithological characters or organic contents, and often by both together. It seems impossi¬ 
ble to adopt any subdivision of strata which shall hold good, and at the same time be easily 
recognizable over wide areas ; and under these circumstances, the more minute are our dis- 
f lam not aware that these two rocks appear in Ohio, although they do in Kentucky, and the name adopted in the Ohio Re¬ 
ports are intended to embrace them. 
t 1 have been disposed to consider the Black slate or shale of Ohio, in some places, as a partial development of the Genesee 
slate of New-York. 
