Chap. XVIII.] DEVONIAN BOOKS IN THE UNITED STATES. 
431 
Judging also from the included organic remains, such as Goniatites iden- 
tical with those of the Duchy of Nassau in Germany, Murchisonia bilineata, 
Productus subaculeatus, Athyris concentrica, and other fossils, M. de Verneuil 
further included in this group the Chemung Rocks, the Hamilton and Marcellus 
Shales, and the Cliff Limestone of Ohio and Indiana (Corniferous and Onondaga 
Limestones). The last-mentioned deposits contain fossil Fishes analogous to 
those of Scotland, besides some characteristic Devonian Shells. Again, the 
occurrence of an Ichthyolite of the genus Asterolepis, associated with forms of 
Spirifer, in the Schoharie Grit of New York, necessarily placed that rock also 
in the Devonian series. 
As fossil Fishes have usually proved the most exact indicators of the age of 
all supra-Silurian rocks, the occurrence, in these Devonian strata, of Asterolepis, 
a genus common in the central Scottish beds of this epoch, and the intermixture 
of other Ichthyolites identical with those of the same country, with Shells of 
the Eifel and of Devonshire, are to me the most convincing proofs that these 
diversified deposits in North America (like those of Russia, the Rhenish Pro- 
vinces, and Devonshire) are simply equivalents, in time, of the very grand British 
deposits called Old Red Sandstone ; for it must be recollected that under this 
term, and particularly in the north-east of Scotland, are included conglomerates, 
sandstones, grey schists, limestones, and flagstones, as well as sandstones of 
both red and whitish-yellow colours — in all, several thousand feet thick (see 
Chapter XI.). 
In one portion of the Canadas, Sir William Logan has estimated the Devonian 
rocks to have a thickness of 7000 feet ; and in the State of New York they 
occupy a more considerable space than the Silurian ; but this Devonian series of 
micaceous sandstones and schists thins out as it passes westwards into the 
States of Ohio, Indiana, and Kentucky, and disappears entirely on the Missis- 
sippi, where the Carboniferous strata repose at once on those of Silurian age. 
3. Carboniferous Rocks. — The Carboniferous rocks are, as is now well known, 
developed in the United States in basins of vaster dimensions than in any part 
of Europe. By the aid of their included fauna and flora, the American strata are 
absolutely identified with the deposits of like age in Europe. Great masses of 
sandstone and schists, once considered to be Devonian, and so coloured in early 
geological maps of the United States, have been shown by M. de Verneuil, 
from their imbedded fossils, to be of Carboniferous age. These masses, which 
are of considerable thickness, form the true base of the Carboniferous rocks of 
North America, and are probably the equivalents of much of the Yellow Sand- 
stone of Ireland, as well as of certain rocks in Westphalia, which were formerly 
classed with the ' grauwacke/ but are now ascertained to belong to the Lower 
Carboniferous beds of the Rhenish Provinces (see p. 402). 
Next follows the Carboniferous Limestone (Mountain-limestone of early English 
viding the Silurian rocks into Lower, Middle, 
and Upper, Dr. Bigsby makes also a triple division 
of the Transatlantic Devonian rocks, analogous to 
that of the European. In addition to many im- 
Sortant inferences respecting the distribution of 
'alaeozoic life, Dr. Bigsby infers that "the Silurian 
and Devonian systems of New York belong to one 
connected period, being the products of successive 
and varying Neptunian agencies, operating in 
waters which deepened westward from the At- 
lantic side, and southward from the Laurentian 
chain on the north. These Palaeozoic groups pass 
one into the other by gradual mineral and zoo- 
logical changes, there being a nearly perfect con- 
formability and a considerable community of 
fossils. The chief break is at the Oriskany Sand- 
stone (base of the Devonian), there being no 
break of like importance at the period of the 
local Oneida Conglomerate (Middle Silurian). 
A division of the Silurian and Devonian systems, 
each into three stages, is based on the change of 
sediment and on the fossil contents. The Middle 
Silurian stage is a period of especial transition, 
from the coarseness of some of its sediments, and 
from their alternations, as well as from the organic 
poverty prevailing." (See the abstract of his 
memoir in the Proceedings of the Geol. Soc. of 
London, No. 5, Session 1857-8 ; also his memoirs 
in full, in the Quart. Journ. Geol. Soc. vols. xiv. 
and xv.) 
