and Commencement of the Mesozoic. 367 
tion; the evidence of a change in the relative position of land 
and sea 
Let us consider, then, in the first place, what is the evidence of 
such phenomena about the termination of the Permian system 
mmencement of the Triassic. 
In every country where these systems exist, so far from there 
being any evidence of disturbance or unconformability about the 
termination of the one and the beginning of the other, there is 
so complete a blending of adjacent strata, that it is only since the 
geological examination of Russia, by Murchison, Verneuil and 
Keyserling, that the Permian beds have been distinguished from 
the variegated marls and sandstones of the trias; indeed, even 
~ ~ day it is hardly decided where the dividing line ought to 
of a luxuriant tropical vegetation? Is it to be compared to the 
apparent coming in of a new order of terrestrial animals? 
If we except the small and rather insignificant genera of G'rij- 
Jithedes and Phillipsia, which occur in the limestone on which 
@ coal measures rest, does it not appear that the entire race of 
trilobites becomes extinct at the termination of the Devonian 
period. Just at the time when this remarkable family of crusta- 
ceans passes away, have we not the strongest proof of a most ex- 
tensive accession of dry land in the luxuriant and extra-tropical 
Vegetation of the carboniferous epoch. Before this period, with 
one or two rare examples, no trace of land plants has been dis- 
covered. If, during the Silurian and Devonian periods, a suita- 
ble climate had prevailed, capable of supporting a terrestrial vege- 
tation, and dry land had existed in a proper position, we shoul 
certainly, long ere this, have obtained marks of its presence. © 
In the Permian system, there have been discovered in Europe. 
at least twelve species of Sauroid reptiles, an order imals 
Which may be regarded as singularly characteristic of the meso- 
Zole period, and imprinting, more than any other race, a peculiar 
type to the mesozoic fauna. If the footmarks observed by Dr. 
King; in the coal measures of Pennsylvania, should prove, as at 
Present suggested, to be referable to some reptile, then the com- 
Mencement of air-breathing reptiles is just coeval with the grand 
Carboniferous flora 
T are certainly strong arguments in favor of placing, not 
only the Permian, but also the Carboniferous group in the meso- 
Zoic period, and terminating the paleeozoic division with the com- 
mencement of the coal measures. 
4 
