INTRODUCTION. r 
According to the views of the American geologists, the Devonian formation in the State 
of New York admits of subdivision into the following minor groups, in ascending order :— 
I. OrntskANY SANDSTONE.—This group consists essentially of coarse siliceous sand- 
stones and sands, sometimes more or less caleareous, sometimes argillaceous, and often con- 
taining nodules, layers and seams of chert. In its greatest development in the State of New 
York, the Oriskany Sandstone has a thickness of no more than thirty feet ; and it is highly 
fossiliferous. According to Sir William Logan (Geology of Canada, p. 360,) the Oriskany 
Sandstone enters Canada at Waterloo, on the Niagara River, and can be traced westward as 
far as the Township of Windham. It does not differ much from the Oriskany Sandstone of 
the State of New York in its lithological characters, except that it is usually more highly cal- 
careous, and in places is a genuine though impure limestone. Its usual thickness is only about 
six feet, though sometimes attaining to as much as twenty-five feet ; andit is often altogether 
wanting, when the Corniferous Limestone reposes directly upon the underlying Lower Helder- 
berg formation. 
The exact age of the Oriskany Sandstone cannot be said to be altogether free from doubt. 
No mechanical break separates the Oriskany and Lower Helderberg deposits, and the differ- 
ence which is observable in the faunz of the two groups is not greater than might be well 
accounted for by the lithological change from the highly calcareous accumulations of the latter 
to the arenaceous sediments of the former period. On the other hand, the Oriskany Sand- 
«stone in the State of New York is succeeded above by an almost non-fossiliferous deposit, the 
so-called “ Cauda-Galli Grit,” which graduates insensibly into, and forms the geological base 
of, the fossiliferous “Schoharie Grit.” Upon the whole, so far as the State of New York is 
concerned, there can be little hesitation in accepting thé views of Professor James Hall, who would 
regard the Oriskany Sandstone rather as the summit bed of the Silurian series than as the base- 
ment bed of the Devonian. Upon this subject, the above-named distinguished geologist thus 
expresses himself :—‘‘ Whatever may be the ultimate decision relative to the line of separation 
between the Silurian and Devonian systems, the base of the Schoharie Grit offers a much more 
decided limitation below, than does the Oriskany Sandstone. The new fauna bears less rela- 
tion to the preceding, and many of the new types are of a strikingly distinct character. In 
the Oriskany Sandstone, we have a considerable number of species which first appear in the 
Lower Helderberg Group ; and the connection between these formations is much more intimate 
than between the Oriskany Sandstone and the Schoharie Grit.”—(Palwontology of New York, 
Vol. LV. p. 3.) 
With regard to the so-called ‘‘ Oriskany Sandstone” of Canada, the case is somewhat 
different. The abundant fauna which it contains is but slightly related to that of the subja- 
