Review of Hall and Whitney's Geology of Iowa. 113 
The Chemung group in the Mississippi valley gives but a 
meagre representation of the same series of rocks in New York, 
Pennsylvania and Ohio. It contains almost an entirely new 
Fauna, although of species closely allied to those of more easterly 
localities of the same group. , 
The passage from the Devonian to the Carboniferous series is 
shown, in this Report, to be an almost imperceptible one, both 
in the physical and paleontological character of the groups, 
there being no strong line of demarcation separating the upper 
calcareous beds of the Chemung group from the Burlington 
limestone, the lowest member of the Carboniferous limestone 
es 
ries. 
_ One of the most interesting facts brought out in this connec- 
tion, is the existence of five distinct members of the Carbonif- 
erous limestone series. These are shown to have been deposited 
m an ocean which was gradually contracting its limits on the 
horth, the greatest development of each successive member of 
the series, in an ascending order, being to the south of the one 
below it; while, subsequent to the deposition of all these and 
‘the sandstone which separates the fourth and fifth limestones, the 
entire area was submerged, allowing the coal-measures to 
posited on the slightly inclined edges of all these limestones, as 
Well as of the Chemung and Hamilton rocks, and also, to some 
extent of the Silurian limestone, after they had been disturbed 
and denuded.* All these limestones of the carboniferous series 
are well characterized by the fossils they contain. 
ntr he 
Pd number of species described from all these rocks is about 
Special attention is given in the Report to the fossils of the 
Carboniferous limestones, as illustrating the successive members 
f th series; and with this object contrasting forms have not 
Selected, but, on the contrary, the more common and char 
acteristic fossils of each rock. Many hitherto believed to be 
identical with European species are proved to be quite distinct. 
_ +¢ number ies of Crinoids, described in the volume, 
's probably equal to or greater than all those before made known 
* See this Journal, [2], xxiii, 187. 
SECOND SERIES, Vo. XXVI, No. 79.—JAN. 1869. 
i. 
