= 
382 L. Lesquereux on the Coal Formations of N. America. 
faculty of migrating developed ina larger degree, have re- 
appeared again and again on the marshes, living there for a 
longer period. 
The field of supposition is unbounded, but it is a field where 
science is not permitted to wander. Where have the new types 
or species come from? How is it, if the disappearance of vege- 
tables like Lepidodendron is only apparent, or local, that we do 
not find any of their remains succeeding the carboniferous 
epoch.* And admitting that species of Lepidodendron have been 
arrested in their migrations on some dry land, should we not 
find above our 4th coal some remains of this genus in the strata 
of sandstone where so many ‘trunks of Psaronius have been 
imbedded. 
I wish that I had time to discuss here at length and with the 
attention which it merits, a subject of importance connected with 
the examition of the stratigraphical distribution of the plants of 
the coal-epoch. Are the coal-measures a single, unique forma 
tion? Do they belong to a single epoch, or are they com 
of a succession of formations separated by immense space 
time, and of which the different stages might be compared to 
those of the recent formations: the Hocene, the Miocene, and 
the Pliocene, for example? In the last case, can we admit the 
vegetation of which the remains have been preserved in the 
shales of the coal, or the vegetation of the coal-marshes, as a true 
representative of the flora of the various epochs where the coal 
was formed ; or was it then, as the bog vegetation is at our time, 
composed of a peculiar group of plants, adapted to the forma 
tion of the coal, pertaining to the marshes only, while another 
* A single specimen of Stigmaria is said to have been found y in the 
odtliegende or Permian. But the locality has not been ascertained at 
quently the statement t be reli oreover for a long time ah ‘he 
i) as I have seen it myself, the Permian in German for 
Beng aay: 
Olds vice-versa, from the difficulty of ascertaining its pos 
and from the want of fossil remains, I cannot take into account as contradicting 
ey ee. Ge ; dron mentioned by Mr. Murchison as found 10 
Permian of Russia, 
