47 
These Devonian rocks contain fossils of the remarkable creatures 
found by the illustrious Hugh Miller—the Cocostehs, Ptericuthys, 
and Cephalaspis—evident relatives and successors of the Pteraspis 
in the upper Silurian. Passing through the mountain limestone 
and coal beds with their ever-increasing variety of fish and 
reptiles, and before the end of the coal period, the marine insects 
and univalve crustaceans crept out of the waters, and finding the 
atmosphere not so much charged with carbon, were followed by 
marine beetles and scorpions, and also batrachian reptiles. Their 
former gills in time disappear; air sacks are substituted in the 
process of their development for their future terrestrial existence. 
After these creatures have emerged from their ocean depths there 
follows a continuous procession of loathsome marine reptiles, 
whose ancient water-breathing apparatus is slowly evolving into 
air respiratory organs, through a persistence on their part to 
ereep out on the sides of the rivers and oceans, till they find it 
more inconvenient to respire through their primitive gills than 
by the aid of their newly acquired organs of respiration. Foot- 
prints of these animals were found in the rocks long before the 
fossils of the creatures themselves. Here is a good illustration 
of Longfellow— 
And departing leave behind them 
Footprints on the sands of time. 
The next rocks, termed the Permian or the New Red Sandstone, 
contain representatives of the batrachian and lizards of the coal 
period, yet this reptilian kingdom is possessed of superior vertebra, 
and better teeth and limbs. We now close with the Paleozoic 
time and enter upon the Mesozoic (middle age), the Triasic, 
Jurasic, and Cretaceous formations. We come in contact with 
flying Lizards, Bats and Vampires, Pteradactyl, &c., the her- 
bivorous, Dinosaniss, and lLabyrinthodents, Crocodiles, &c. 
Higher still we arriye at bird-lke lizards, the Iguanodon, 
Hadrosaurus, and Magalosaurus. There are also lizard-like 
birds with beaks and peculiar wings, the Hesperornis, Odon- 
topteryx, and the Archeopteryx. Also we come to the 
Ornithorincus, the predecessor of the hairy Marsupial, or pouched 
animal, the link that connects the egg-laying or oviperous animal 
with the true Mammalia. Here we approach the most interesting 
part of the process of evolution. Previously life had been 
generated by the dividing of cells; egg-laying and implacental 
forms only; and now lastly, the process which culminates in 
bringing the young into the world alive, the Mammalia. During 
_ these changes on land many wonderful cases of reptilian develop- 
. 
j 
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ment had taken place in the sea, the scaley Saurians, the 
Plesiosaurus, Ichthyosaurus, and the Elasmosaurus, the last 
monster being no less than 50 feet in length. The vegetable 
kingdom had during these great intervals been gradually evolving 
