116 Dr Fleming on the Revolutions in the Animal Kingdom , 
fined. A vast number of fossil species, therefore, remain unex- 
plored in the equatorial and antarctic regions, the characters of 
which will either confirm the view which is here given, or fur- 
nish evidence for that alteration of climate, occasioned by a 
change in the obliquity of the ecliptic, or in the Earth’s axis of 
rotation, which a few naturalists believe to have taken place. If 
the fossil animals at the Equator do not resemble recent or fos- 
sil Arctic productions, but exhibit characters peculiar to them- 
selves, it will be necessary to abandon the idea of great astrono- 
mical revolutions, and content ourselves with investigating the 
changes organised beings are experiencing at present, in order 
to discover those circumstances which have impressed on the 
fossil species their peculiar outlandish character. 
3. The opinion entertained by Werner, that the petrifac- 
tions of the older rocks belong to animals of more simple struc- 
ture and less perfect organisation, than those which occur in the 
recent deposits, is, when considered in a very general point of 
view, an approximation to the truth. In the beds of the transi- 
tion class (the oldest rocks which are known to contain petrifac- 
tions), the remains both of radiate and molluscous animals oc- 
cur ; yet the organisation of the latter is considered more per- 
fect than that of the former. In the transition class, however, 
no remains of vertebrose animals have been detected. In the 
independent coal-formation (one of the oldest groups of the 
floetz-class), in addition to the relics of radiate and molluscous 
animals, those of several annulose animals occur, as species of the 
genera Trilobites, Dentalium and Spirorbis ; together with 
fishes, both osseous and cartilaginous. In the newer groups of 
the floetz series, relicts of amphibia make their appearance, and 
in the newest groups those of birds and quadrupeds. In the 
oldest alluvial deposits are. found the bones of extinct quadru- 
peds ; in the newer beds, those of such as still survive. From 
the period, therefore, at which petrifactions appear in the old- 
est rocks, to the newest formed strata, the remains of the more 
perfect animals increase in number and variety ; and it is equal- 
ly certain, that the newest formed petrifactions bear a nearer re- 
semblance to the existing races, than those which occur in the 
ancient strata. The older remains are much altered in their tex- 
ture, and more or less incorporated with the matter of the rock* 
