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Notes upon the Geology of the Western States. 61 
New York. This mass is the ‘blue limestone,” of Prof. Locke, 
in the Ohio reports, but not, as has been supposed, a member of 
the Mohawk group, but a limestone and shale series, represent- 
ing what in New York is a shale and sandstone group. The 
fossils are essentially the same. Pterinea carinata, Cyrtolites or- 
natus, Bellerophon bigketas, Leptenh ? ‘Trinuchtus; and 
Graptolites, are the fossils whic li 
the same place in New York. Two or more species rob: Isote 
_ frequently found in the same rocks. The Isotelus in New * ne ' 
isa characteristic fossil of the Trenton limestone. This group 
is well developed, forming high, abrupt cliffs on the Ohio below 
Portsmouth, and at Cincinnati ; also at Maysville, Ky. and Mad- 
ison, Ind. At either of these places many other fossils are found 
besides those enumerated. In the higher beds are Delthyris and 
Orthis, one species of the latter gems the same as occurs in the 
Niagara group in New York. 
- At Newport, Ky. opposite to Cincinnati, and at one or two 
other places in this vicinity, there is a green shale with the Tri- 
arthrus, Graptolites, and a few encrinal joints, shewing the same 
assemblage of fossils and in the same position as the “ Utica 
slate” of New York. The rock below this, which is seen in 
place only during low water of the Ohio, is a shaly limestone, 
with shells and great numbers of the fragments, with sometimes 
perfect specimens of the Isotelus; Dr. Locke of Cincinnati has 
a very large individual of this genus. This rock is probably the 
equivalent of the Trenton limestone of New York. 
~ The Ontario and Mohawk groups are both seen on the Missis- 
sippi above Dubuque, containing as elsewhere, a large number of 
fossils.* At the same place and below these rocks, there is a mass 
of sandstone, but I have not been able to identify it with any 
mass farther east. 
_ My examinations were not extended far enough to the north 
to discover the lower members of the transition or Silurian sys- 
tem, which doubtless would be found there, 1 have sufficient 
data to feel entirely satisfied of the results of these examinations 
as here given.» These may be of some use, particularly as re- 
gards es readers of the geological reports, where it is not only 
desirable to give extended views, but also to explain, as far as 
eps! the rocks now known by different names. 
ay is ie ts tlle ples ech shines dean mei egal. 
