Acidic Erupfices of yorlheasfern Maryland. — Keijes. 39 
of the Utiea slate,* remarking that the presence of Lingula' 
of a large and a small species, enhances the resemblance. 
Prof. J. D. Wliitney, in reporting on the lead mines of Wis- 
consin! ^^ 1802, dwells at length on the carbonaceous charac- 
ter of the Hudson Kiver shales, which are said to show some- 
times "faint graptolitic markings." 
"Tlie presence of carbon ill tlu- shales of tlic Hudson River group 
over , so extensive an area, and in siicli larur (piantity, is a matter of 
considerable interest, both practically and scientifically: it seems 
hardly possible that a material existing- in such abundance and con- 
taining from one-tenth to one-fifth its weight of bituminous and carbon- 
aceous substances, should not at some future time be utilized for light- 
ing or heating purposes, in a region where coal does not occur," p. 184. 
The suggestion that the Utica slate horizon is to be sought 
for in the beds overlying the Galena is confirmed by later de- 
velopments in the oil regions of Indiana and Ohio where the 
Utica slate is recognized at the bottom of the Hudson River 
formation, and yet where the underlying "Trenton" is a po- 
rous dolomite, not unlike the Galena limestone. In fact it 
has been found that in many cases the fossils which in the 
upper Mississippi valley are found in the Galena, in Kentucky 
and Tennessee are said to come from the Trenton limestone. 
It may therefore be considered that the Galena limestone is 
only a phase of the Trenton, intensified in the typical region, 
and fading out in all directions. It is a convenient designa- 
tion in Iowa and some parts of >Yisconsin and Illinois, but in 
Minnesota its convenience hardl}"^ warrants its continued use. 
The physical break and the faunal change which follow it, in 
the Northwest, are the probable parallels of those which mark 
the transition from the Trenton to the Hudson River (Utica 
slate) horizon to which Mr, Walcott has called attention. 
J/rt// -5, 189Jf. 
ACIDIC ERUPTIVES OF NORTHEASTERN 
MARYLAND. 
By Charles Rollin Keves, Jetteison City, Mo. 
For several years prior to his peculiarl}^ sad and untimely 
death, a few months ago, the late professor George H. Wil- 
*Goology of Iowa, vol. i, part I, p. (57, 185S. 
flleport on the Geological Sur\-e\- df Wisconsin, vol. i, .bimes Hall 
and .1. 1). Whitnev, \^{Vl. 
