PALAEONTOLOGY OF NEW-YORK. 
and up this river as far north as the Falls of St. Anthony in Minnesota. 
In Wisconsin, Iowa, Illinois and Missouri, the same formations are reco¬ 
gnizable, and everywhere marked by a few peculiar species. In Kentucky, 
the same is true of these limestones; and even in Tennessee, where the 
great tenuity of all the older rocks causes an apparent mingling of several 
formations, these divisions are still to be recognized. 
From the St. Mary’s river on the north, to the Mississippi, I have 
personally examined these beds at numerous points, as likewise in the 
southern part of Wisconsin, in Iowa and Illinois; and though the thick¬ 
ness of each member is rarely more than a few feet, I have never failed 
to recognize more or less clearly the lithological characters by which each 
is known in New-York, and likewise some of the more characteristic 
fossils. When followed in a westerly or northwesterly direction, there 
appears to be a gradual thinning out of these deposits, an increase of ar¬ 
gillaceous matter, and an almost entire absence of the corals proper; a 
few of the Bryozoa still continuing. This fact is in harmony with the 
conditions affecting the Chazy limestone, which thins out, as before stated, 
somewhere in the vicinity of the Escanaba river, on the north of Lake 
Michigan. 
The Trenton limestone proper, which gives character to the entire 
period, is the most persistent of the different calcareous members. Large 
accessions have been made to our knowledge of its extension and character 
in other parts of the country, since the publication of the first volume of 
the New-York Palseontology. The Geological Survey of Canada has shown 
its wide extent upon the north and northwest, both in the Lower and 
Upper Provinces. In its western extension, it shows, in like manner with 
the limestones below, a gradual diminution in thickness, a larger proportion 
of intercalated shaly laminae and beds, and a decreasing number of fossils. 
Nevertheless it maintains sufficiently its lithological aspect to be recognized 
everywhere ; and even throughout the entire distance from the Hudson 
to the Mississippi, it contains enough of its characteristic fossils to be 
identified. It is well marked on the northern shores of Lake Huron and 
