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NATURAL SCIENCES OF PHILADELPHIA. 109 
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Descriptions of New Species of FOSSILS, from the Marshall Group of Michi¬ 
gan, and its supposed equivalent^ in other States; with Notes on some 
Fossils of the same age previously described. 
BY PROFESSOR ALEXANDER WINCH ELL. 
The following paper is intended to constitute a further contribution to our 
knowledge of certain western rocks occupying a position near the boundary 
line between the carboniferous and Devonian systems.* The materials for 
this paper have been in part collected by the writer in Michigan, Ohio, Indi¬ 
ana, and Iowa. Further material has been found amongst the investiganda 
of the “ White Collection ” of the University of Michigan. Col. Charles Whit¬ 
tlesey’s collection of fossils from the “ Fine Grained Sandstone ” of Ohio, has 
also been placed in the writer’s hands for study. In addition to this, the lat¬ 
ter has spent several days with Prof. James Hall in his cabinet, engaged in 
making direct comparisons between the fossils of the rocks under considera¬ 
tion, and the types of the Chemung group, preserved in his magnificent col¬ 
lection. An opportunity has also been enjoyed of making a hasty survey of 
the fossils from the same horizon, contained in the extensive collection of the 
Illinois Geological Survey, for which the writer’s acknowledgments are due to 
the Director, A. H. Worthen, Esq. 
The reader will observe that all the identifications heretofore made with 
typical Chemung fossils from New York and Pennsylvania, have been aban- 
* Former papers by the writer, on the same subject, may be referred to as follows: “ First Bien¬ 
nial Report” of the Geological Survey of Mich. I860 ; Amer. Jour. Sci. and Arts, [2J Yol. xxxiii. p. 
352; ib. [2j xxxv. p. 61; Proc. Acad. Nat. Sci. Phil., Sept. 1862, p. 405; ib. Jan. 1863, p 2. 
1865 .] 8 
