PALAEONTOLOGY OF NEW-YORK. 
2 
known to us the existence and wide extent of a sandstone, which he at 
that time regarded as far below the Potsdam sandstone of New-York. 
This rock, moreover, charged with lingulae, trilobites, etc., showed a much 
more prolific fauna than the Potsdam sandstone was at that time known 
to contain. A personal exploration in 1850, and an examination of the 
localities named by Dr. Owen, enabled the writer to place this rock in the 
same horizon with the Potsdam sandstone, and in fact to demonstrate its 
continuity with the more eastern deposit of this age, by tracing it along 
the lower limits of the Silurian basin, from Canada West on Lake Huron, 
to the Mississippi and St. Croix rivers in Wisconsin. 
The results of these examinations were published, under the writer’s 
own name, in the Report of Messrs. Foster and Whitney upon the Lake 
Superior Land District in 1851. 
Dr. Owen subsequently adopted this view of the age of the sandstone, 
and has thus published it in his final Report in 1852. 
The great interest of this formation in the west, is the occurrence of 
several species of trilobites in beds which mark certain horizons in the 
formation. The trilobites are referred by Dr. Owen to several genera which 
he has constituted to receive them, though the forms in many instances 
bear strong resemblances to known genera. The broken and comminuted 
remains of these trilobites are distributed over an extent of more than 
two hundred miles along the Mississippi river in greater or less profusion; 
and they are every where found, until the sandstone disappears beneath 
the river in the northern part of Iowa. 
The lingula beds are almost equally extended, though not so prolific in 
all parts of this range. At the falls of the St. Croix river, more than half 
the material of the rock appears to be composed of these shells. Towards 
the south, the beds still continue; but the shells are broken and com¬ 
minuted, and are drifted together precisely in the same manner as we find 
seashells upon a modern beach. Here, again, over this wide area, and a 
thousand miles from the eastern known limits of the sandstone, we find 
the most unequivocal evidences of a shallow sea. 
