112 A POPULAR, EXPOSITION. OF THE 
Above the deposits of the Azoic Age,. various. sandstones, lime 
stones, slates and other strata, in which organic remains first appeary. 
are recognized, as forming the second geological series, and are known 
collectively as Paleozoic Rocks. ‘The term “ Palzozoic,” signifying: 
“ ancient life,’ is bestowed on these strata in allusion.to the marked; 
difference. which prevails between their organic. types, viewed. as: 
a. whole, and. those belonging to existing Nature. Among: the: 
more remarkable extinct forms of the Paleozoic, Age, Graptolites; 
Cystideans, numerous Brachiopods, Orthoceratites, Trilobites, and: 
some peculiar fishes, hold a prominent place. Reptilian, types are; 
rare, and of comparatively low organization ; and Mammalia appear, 
to have been entirely absent. In Canada, the lower members of the; 
Paleozoic strata are largely developed, but. the higher divisions of the: 
series are of only partial occurrence, or are altogether wanting. 
The strata of a succeeding series; still ascending in the geological: 
scale, are known as Mesozoic or Secondary Fossiliferous Rocks. Their: 
organic remains are quite distinct from those which occur in the: 
underlying formations. Ammonites aud Belemnites, with highly 
organized reptilian types, including the Ichthyosaurus, Plesiosaurus, 
Pterodactyl, Iguanodon, &c., are among their more characteristic and 
extinct forms. Fishes with equally-lobed tail-fins, and others with 
scale-coverings similar to those of the great majority of fishes which. 
inhabit our present waters, first appear in. the deposits of this Secon- 
dary Fossiliferous Age. Mammalian types are all but unknown,and 
those hitherto discovered, are of low organization. In Canada, the 
Mesozoic rocks are without. representatives. 
The Cainozoic or Tertiary Fossiliferous Strata succeed the Meso- 
zoic. In these, the organic remains closely approximate to the 
forms of the present epoch. Amongst. the mollusca, brachiopods bee, 
come scarce, and. cephalopods with. chambered. shells, haye greatly 
diminished. Those with foliated septa (as ammonites, baculites, &c.) 
have entirely disappeared, together with the huge and abnormal rep- 
tiles ot the Mesozoic Age. Mammalian. types, on. the other hand, 
are fully represented—examples of all existing orders, with the ex-. 
ception of that in which Man is alone included, being met.with in. 
these deposits. In Canada, however, the Cainozoic formations, do. 
not, occur. 
Finally, a still higher series of. deposits, partly merging into the, 
Cainozoic, where these.occur, and in part consisting of the products; 
of existing causes, may be classed together under the term, of Post-, 
