372 C. A. White—Fossil Faunas and Floras. 
the Laramie, admits of no doubt as to their lacustrine origin. 
I have therefore referred to these as intra-continental deposits, 
and to the remains which they bear as those’of continental 
faunas and floras, as contrasted with marine faunas. The term 
sea coast deposits is used in contrast with the forementioned 
term which is applied to the other deposits, and by it is of 
course meant the well known marine strata, the order of super- 
position of which can be more or less satisfactorily traced from 
the earlier to the later geological epochs. 
Because of the isolation of the intra-continental deposits 
they can have no place in any observed order of superposition 
among marine deposits, and for this reason they must there- 
fore be studied separately. The great difference also between 
the aqueous faunas of the fresh and brackish waters respec- 
tively in which the former deposits were made, and those of 
marine waters, makes a chronological comparison of the two 
categories of deposits, by such means, a matter of great uncer- 
tainty. This is an additional reason for their separate study 
until satisfactory data can be obtained for their correlation with 
marine formations. While I believe that such correlation, if 
ever effected, must be based mainly upon paleontological data, 
we ought to expect much aid from lithology and physical 
geology, especially when studied in connection with paleon- 
tology. 
Pursuing a consideration of the latter subject we may rea- 
sonably infer that certain species among the land faunas and 
floras have occupied the region between any given inland 
sea or lake on the one hand, and the open. sea on the other, 
across the whole intervening region, unless there were known 
physical obstacles to such dispersion. Therefore the remains 
of such species might easily occur in beth inland and coast 
deposits. That is, remains of the same species of land animals 
and plants may have been entombed in lacustrine deposits on 
the one hand and estuary deposits along the sea coast on the 
other, the species having occupied the whole of the interven- 
ing Jand area. The contemporaneity of such deposits would 
be thereby apparent; and in my estimation such evidence 
would be more conclusive than any other. 
Still, as a matter of fact, no correlations of intra-continental, 
with sea coast deposits of North America have yet been accom- 
plished either by such means, or by any other practical method. 
It is nevertheless true that most of the authors who have writ- 
ten upon the formations in question have referred both the 
inland and sea coast series to respective subdivisions of the 
geological scale which was originally established for Hurope, 
and supposed to be of universal application, with a confidence 
which is only warranted by positive knowledge. For example, 
