388 Marcou’s Geological Map of the United States. 
similarity indicates a Carboniferous age rather than ‘Triassic, 
The limit of the formation above or below, although perhaps 
well defined at one point, may not be at others, or may be very 
different; the red color of the strata—the only guide—being the 
result of chemical changes and not of original deposition. The 
lower limit is not clearly defined, and there are no outcrops 
or uplifts of the strata sufficient to reveal the whole series. The 
thickness, therefore, cannot be accurately stated. 
The entire absence of fossils from these strata, so far as known, 
Permian, or either of them, as Triassic alone. It would be most 
separate geological a Whitney and Foster with 
ames Hall, by D. D. Owen, and by Sir 
cious attempt at generalization which has seldom been equalled. 
The fact that Mr. Marcou’s map is widely circulating in Europe 
just such American Geology as this, has made it the duty of 
the science of the country to protest against its being acce ted 
abroad, notwithstanding its publication under the sanction of the 
logical Society of Psion: | 
