Fossils from the Lower Coal Measures — Keyes. 25 
Coal IJ^feet. 
Shale 15 " 
€oal 4 " 
A boring near Mitchellville at the eastern border of the 
county shows an ahiiost entire absence of coal; a statement of 
the material passed through is also given, though in a different 
form, in the second biennial rej^ort of the state mine inspector. 
feet, inches. 
Drift 64 
Blue and black shales 17 6 
Impure coal 1 2 
■Gray, black, blue and sandy shales with two layers of sandstone 141 7 
Limestone with marly partings 39 6 
Coals No. 2, and especially No. 3, are the most profitably 
worked, and furnish nearly all the coal mined in the county. 
Immediately overlying and thus forming the roof of coal No. 3, 
is a soft black clayey shale, sometimes slaty in places, highly 
fossiliferous and containing much iron pyrites in the form of 
<:rystals and nodules; many cubes of the former being over an 
inch along the edges, and the latter often containing shells of 
mollusca. The shell substance of the fossils from these shales, 
aside from those contained in the pyritiferous nodules, is re- 
placed more or less completely by pyrite. In some specimens 
the replacement is complete, in others only a thin film of pyrite 
■covers the shell leaving the interior of the shell substance with 
the original calcareous constituents; betw^een the two extremes 
all degrees of replacement by pyrite occur. In a few instances 
— Lophophylhun, fish-teeth, and remains of crinoids — no re- 
placement has taken place. The following tabular synopsis of 
the fossils thus far discovered and identified will illustrate the 
jinore important faunal features of the shales under consideration: 
I^ossils collected at Des Moines. 
(The figures in parenthesis refer respectively to the number 
of genera and species in each group). 
CffiLENTERATA. (2-2). Disciua nitida, Phillips. 
■Lophophvllum proliferum MeC. Productu« nanus Meek and Worthen. 
■fihombopora iepidodendroides Meek. muric^tus N and P. 
EcHiNO DKBMATA. (1-1). Chonetes mesoloba N and P. 
Eupachycrinus (sp?) (nov. sp.) 
,. ,,rvi-v Streptorhvnchus crenistna Phillips. 
^ ERMBS. ( lO-lo) . Spirifera camerata Morton. 
Bryozua. (1-1). lineata Martin 
Synocladia biserialis, Swallow. ,. . ., . rockyinontanus Marcou 
^. ,. , ',,> Spinfenna kentuckeiisis Shuinard. 
lirachiopoda. (9-14). Athyris subtilita Hall. 
Lingula umhouata Cox. Retzia mormoni Marcou. 
