40 
PALEONTOLOGY OF NEW-YORK. 
to the westward*, hut extending with great force through New-York, 
Pennsylvania, Maryland and Virginia. 
This sandstone is charged with great numbers of peculiar fossils : 
Brachiopoda of larger size than those of the preceding strata occur in 
immense numbers, so that the rock is often a complete mass of these 
shells. In some places, Gasteropoda of the Genus Platyceras occur in 
such numbers, and in such positions, that they could only have been 
so placed from being drifted together by gentle currents; for these 
shells, thin and fragile like the modern Janthina (to which family they 
belong), are preserved in great numbers in what are termed “ pockets,” 
packed together in loose sand, which, in some places in Maryland and 
Virginia, is no more coherent than the sands of a modern sea-beach. 
These gasteropods, moreover, assume so great a variety of form and 
modification of parts, that it often becomes extremely difficult to dis¬ 
tinguish specific differences or generic relations. 
We have at this period a profusion of individuals, represented by few 
species of this class of animals, to which we have no parallel in any of 
the palaeozoic groups; while the preceding and following formations 
nearly equal this in the abundance of individuals, and present a larger 
number of species. 
Certain bracliiopods, not known till the period of the Lower Helder- 
berg group, acquire, in the Oriskany sandstone, a development truly 
astonishing; and two genera, at least, attain at this time their acme, 
and in the next period gradually decline. In the Oriskany sandstone 
we meet, for the first time, so far as would appear from our New-York 
formations, Spirifers with bifurcating costae; a character ever afterwards 
exhibited in some species of each succeeding period, and peculiarly 
marked in those of the Carboniferous limestones and Coal measures. 
M. de Verneuil, and other European geologists, have been inclined to 
place the dawn of the Devonian period in the horizon of the Oriskany 
sandstone, and to regard this and the succeeding rocks as separable 
* The Oriskany sandstone continues westward, with some slight interruptions, to Cayuga lake; beyoud 
which, it has been found only in isolated patches. 
