If we turn to the same geological record to trace the development of animal life, we find it running a parallel course with that of plants. The earliest known fossil, the Eozoon Canadiense, from the Lower Laurentian, is that of the chambered shell of a protista of the class of Rhizopods, whose soft body consists of mere protoplasm which has not yet differentiated into cells. As we ascend the scale of the primordial era, traces of marine life of the lower organisms begin to appear, until in the Silurian they become very abundant, consisting however mainly of mollusca and crustacea, and in the Upper Silurian we find the first traces of fishes. In the Primary era the Devonian and Permian formations are characterised by a great abundance of fishes, of the antique type, which has no true bony skeleton, but is clothed in an armour of enamelled scales, and whose tail, instead of being bi-lobed or forked, has one lobe only—a type of which the sturgeon and garpike are the nearest surviving representatives. In the Coal formation are found the first remains of land animals in the form of insects and a scorpion, and a few traces of vertebrate amphibious animals and reptiles; while higher up in the Permian are found a few more highly developed reptiles, some of which approximate to the existing crocodile. Still fishes greatly predominate, so that the whole Primary period may be called the age of fishes, as truly as, looking at its flora, it may be called the age of ferns. In the Secondary period reptiles predominate, and are developed into a great variety of strange and colossal forms. The first birds appear, being obviously developed from some of the forms of flying lizards, and having many reptilian characters. Mammals also put in a first feeble appearance, in the form of small, marsupial, insectivorous creatures. In the Tertiary period the class of mammals greatly predominates over all other vertebrate animals, and we can see the principal types slowly developing and differentiating into those at present existing. The human type appears plainly in the middle Miocene, in the form of a large anthropoid ape, the Dryopithecus, and undoubted human remains are found in the beginning of the Quaternary, if not, as many distinguished geologists believe, in the Pliocene and even in the Miocene ages.