Mineralogy and Geology. 355 
un 
other localities, resembling in all respects that of Leclaire, and holding 
many of the same fossils. It is likewise underlaid by the even-bedded 
darker-colored limestone, bearing Halysites catenulatus, Pentamerus ob- 
8,and many large Orthoceratites, which are everywhere regarded 
as evidence of the Niagara age. I could not hesitate, therefore, to par- 
allelize the succeeding beds with the limestone of Leclaire, though we had 
failed to trace it across the country in a continuous outcrop. At the 
same time, on critical examination of the collection of fossils made at 
Racine and at some other points, I detected many species known as char- 
acteristic of the Niagara formation in the State of New York, requiring 
its recognition as a member of that group (rather than of the Onondaga- 
salt group), and uniting with it, as identical in position, the Leclaire 
tone.” 
we At the same time, we have recognized, from Racine and adjacent local- 
hes, including Leclaire in Iowa and a single locality in Illinois, the fol- 
identical with or closely allied to M. mylitta (Billings), an undescribed 
Murchisonia from Racine identical with one from Galt, Subulites ven- 
tricosa, Pleurotomaria solaroides? Loxonema longispira, besides other 
forms which are closely allied to species of the Guelph limestone. 
each other, while their relations with the Onondaga-salt group, though 
sry intimate in the single locality in Central New York, become less and 
lese conspicuous in a westerly direction. 
a] isconsin, p- 67, 1861. 
ay BS eee dan Tiare" geen inated the thickness of the lime- 
stone at Leclaire from the presence of lines of false bedding, but I have had no op- 
~ Unity for a re-examination of the locality- ; 
