INTRODUCTION. 
3 
The Cambrian Age, or the secondary period of the Palaeozoic, is remarkable for the prolific 
growth of sea-weeds which then flourished, but animal life was plentiful, somewhat more developed, 
though none of the creatures of this period were provided with a back-bone. The species most 
numerous were two crustaceans, viz., the trilobites (three-lobed creatures), and an animal resem¬ 
bling the horse-shoe crab. 
The two Silurian Ages are distinguished as being the periods when mollusks were most 
numerous ; of the fossils found everywhere through these strata, those species having soft bodies are 
most plentiful, such as the snail, nautilus, and other species of the cuttle-fish. In the Upper Silu¬ 
rian, trilobites begin to diminish and corals to appear, also forms of crinoids, or animals that were 
so nearly vegetable that they are called stone-lilies. There were also several land plants of the fern 
species, and a few vertebrate sea-animals of the shark kind. 
In the Devonian Age fishes appeared in the greatest abundance, their fossil bones being so 
numerous that it has been called the “ Age of Fishes.” However, these primary fishes presented 
great simplicity of structure, as compared with those of the present period. Their bones were 
imperfect, and instead of scales the body was covered with shield plates. Land plants now showed 
greater exuberance of growth and developed into forests. 
The Carboniferous Period shows another remarkable change. The forests had become so 
rank, under the effects of warm vapors and fruitful soil, that the earth became cumbered with an ex¬ 
cess of vegetation, which in decaying formed immense beds in marshy districts. These beds were 
gradually covered by new growths, and were converted into bituminous coal. This first conver¬ 
sion, by the action of heat, was subsequently transmuted into anthracite, graphite, and other min¬ 
erals. The forests were much larger, though still retaining the fern characteristic, and new forms 
of vegetable growth appeared in giant canes and club mosses. It was during this period, too, that 
amphibians made their first appearance, forming a connecting link between fishes and reptiles. 
Insects also came into being now, to people the rank and lofty forests. 
The Mesozoic Era was the period of giant reptiles, existing in great numbers and of monster 
size, such as the teleosaurus, ichthyosaurus, megalosaurus, pterodactyl, and other flying, swim¬ 
ming and creeping creatures, some of which were more than fifty feet in length, and of propor¬ 
tionate bulk. 
In the Triassic Period first appeared creatures bird-like in form, the impressions of whose 
feet and three toes are to be seen in the sandstones of some valleys in Connecticut and New Jersey. 
A few mammals, of a very low type, also came into being during this era. 
The Jurassic Age is particularly interesting for being the period when reptiles of ferocious 
aspect and appalling size predominated, wherein we observe a connecting link between reptiles and 
birds, as we shall show in the body of this work. 
The Cretaceous Period is distinguished for being the last stratum of which the fossil 
animal remains are wholly of extinct species. The group is subdivided into upper and lower, 
called the chalk and greensand formations, which are widely distributed over both continents. 
Thus at widely separated points in the ancient seas of four continents were similar deposits pro¬ 
duced during the same geological period, characterized by the animal remains which they include 
.of the same general type, and often of the same species. The ichthyornis, or fish-bird, made its 
appearance during this period. This curious creature had the back-bone of a fish, a keel-like 
breast-bone, and a long, slender beak, which was armed with socketed teeth. It was equal to a 
pigeon in size, 
The Neozoic Era represented a change no less remarkable than that of the Mesozoic, for as 
the latter gave birth to giant reptiles, so it was during the Neozoic period that these huge crea¬ 
tures disappeared to give place to higher orders of species, and were accordingly succeeded by 
mammals. Birds developing from the pterodactyl and the ramphorhynchus, the primitive forms, 
also now appeared, and the land became peopled with creatures whose forms resemble those by 
which we are now surrounded. 
