. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. THE LAURENTIAN AND HURONIAN PERIODS. 69 penter and Dawson, from the standpoint that it is a genuine organism—the balance of evidence up to this moment incHn- ing decisively to this view. The structure known as Eozoon is found in various localities in the Lower Laurentian limestones of Canada, in the form of isolated masses or spreading layers, which are composed of thin alternating laminae, arranged more or less concentrically (fig. 22). The laminae of
. The ancient life-history of the earth; a comprehensive outline of the principles and leading facts of palæontological science. Paleontology. THE LAURENTIAN AND HURONIAN PERIODS. 69 penter and Dawson, from the standpoint that it is a genuine organism—the balance of evidence up to this moment incHn- ing decisively to this view. The structure known as Eozoon is found in various localities in the Lower Laurentian limestones of Canada, in the form of isolated masses or spreading layers, which are composed of thin alternating laminae, arranged more or less concentrically (fig. 22). The laminae of these masses are usually of different. Fig. 22.—Fragment of Eozoon, of the natural size, showing alternate lamincE of loganite and dolomite. (After Dawson.) colours and composition ; one series being white, and com- posed of carbonate of lime—whilst the laminae of the second series alternate with the preceding, are green in colour, and are found by chemical analysis to consist of some silicate, generally serpentine or the closely-related " ; In some instances, however, all the laminae are calcareous, the concentric arrangement still remaining visible in consequence of the fact that the lamina are composed alternately of lighter and darker coloured limestone. When first discovered, the masses of Eozoon were supposed to be of a mineral nature; but their striking general resem- blance to the undoubted fossils which w^ll be subsequently spoken of under the name of St7'oinatop07'a was recognised by Sir William Logan, and specimens were submitted for minute examination, first to Principal Dawson, and subsequently to Dr W. B. Carpenter. After a careful microscopic examina- tion, these two distinguished observers came to the conclusion that Eozoon was truly organic, and in this opinion they were afterwards corroborated by other high authorities (Mr W. K. Parker, Profesor Rupert Jones, Mr H. B. Brady, Professor Giimbel, &c.) Stated briefly, the structure of
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