In the Primordial or oldest fossiliferous rocks next in succession to those great Eozoic formations in which protozoa alone have been discovered, we find the remains of crustaceans, mollusks, and radiates--such as shrimps, shell-fish, and starfishes--which appear to have inhabited the bottom of a shallow ocean. Among these were some genera belonging to the higher forms of invertebrate life, but apparently as yet no vertebrated animals. Fishes were then introduced, and have left their remains in the upper Silurian rocks, and very abundantly in the Devonian and Carboniferous, in the latter of which also the first reptiles occur, but are principally members of that lower group to which the frogs and newts and their allies belong. The animal kingdom appears to have reached no higher than the reptiles in the Palaeozoic or primary period of geology, and its reptiles are comparatively small and few; though fishes had attained to a point of perfection which they have not since exceeded. There was also, especially in the Carboniferous age, an abundant and luxuriant vegetation. The Mesozoic period is, however, emphatically the age of reptiles. This class then reached its climax, in the number, perfection, and magnitude of its species, which filled all those stations in the economy of nature now assigned to the mammalia. Birds also belong to this era, though apparently much less numerous and important than at present. Only a few species of small mammals, of the lowest or marsupial type, appear as a presage of the mammalian creation of the succeeding tertiary era. In these two geological periods, then--the Palaeozoic and Mesozoic--we find, first, the lower _sheretzim_ represented by the invertebrata and the fishes, then the great reptiles and the birds; and it can not be denied that, if we admit that the Mosaic day under consideration corresponds with these geological periods, it would be impossible better to characterize their creations in so few words adapted to popular comprehension. I may add that all the species whose remains are found in the Palaeozoic and Mesozoic rocks are extinct, and known to us only as fossils; and their connection with the present system of nature consists only in their forming with it a more perfect series than our present fauna alone could afford, unless, indeed, we should find reason to believe that any modern animals are their modified descendants. They belong to the same system of types, but are parts of it which have served their purpose and have been laid aside. The coincidences above noted between geology and Scripture may be summed up as follows: