180 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 3, NO. 4. 
and there insued a period of dessication as shown by the salt and 
gypsum beds, the prevailing red color of the rocks and the lack 
of wide spread marine deposits. Applying at this point Cham- 
berlins theory that the exposure of land masses with their con- 
sequent degradation meant the extraction of large quantities of 
C0 2 from the air and a subsequent period of refrigeration if not 
glaciation it will be seen that the advent of the reptiles in the late 
Carboniferous and the Permian was coincident with the appear- 
ance of large land masses and a decided climatic change from that 
in which the amphibians flourished ; almost as great as the change 
from the habitat of the fish to that of the amphibian. The 
amphibians had carried their specialization very far in the watery 
environment but the elevation of the land and its dessication pro- 
duced a series of new possible contacts which permitted the vari- 
ables of the amphibians to establish themselves as land reptiles. 
Then began the wonderful growth of the reptiles in Triassic and 
Jurassic time which soon so crowded the land that by the middle 
Tiias, the Muschelkalk, when the waters gained a slight ascend- 
ency over the earth for a time the variables of the land reptiles 
returned under new forms to the waters which became crowded 
with the Kothosaurs, Plesiosaurs and even Ichthyosaurs. With 
the wide spread Jurassic seas the Ichthyosaurs were abundant and 
so the Mosasaurs of the Cretaceous seas but just as today, the en- 
vironmental monotony of the oceanic environment for air- 
breathing animals kept down the number of variables which es- 
tablished themselves, i. e. the species, though the individuals 
multiplied beyond number. 
