Eozoon (Gr. #<5f, dawn, and fwov, animal), a name given to certain forms found in the Laurentian rocks of Canada, Massachusetts, and other primordial regions, under the belief that they are the impressions of the earliest animal organisms which appeared on the earth. The serpentine rock in which they are found is far older than the lower Silurian, in the azoic series of authors; if these are of organic origin, they carry back the first appearance of animal life to a period much earlier than geologists have usually admitted. Dr. Carpenter, Dr. Dawson, and others regard the so-called eozoon Canadense as a protozoan, of the rhizopod or foraminiferous division, a jelly-like living mass, spreading over the bottom of the sea, secreting calcareous partitions, and thus forming small chambers or cells, the interior of which has been filled with serpentine deposited from the waters of the ocean. Dr. Dawson believes that it had several foramini-feral successors in these early periods. On the other hand, excellent microscopists and mineralogists deny its animal origin, and maintain that these are only imitative forms of inorganic material, the result of infiltration of waters and chemical agency.

Specimens have been found in the limestone or serpentine of Newbury and Chelmsford, Mass., in semi-crystalline vein-like deposits in granitic gneiss, in isolated masses, and not in stratified deposits accessible to fossils. High authorities are enlisted on each side, but the evidence seems to preponderate on the side of its animal origin. - The term eophyton has in like manner been applied to what appear like the remains of a terrestrial flora found in Swedish rocks of eozoonal age; they seem like stems and long parallel-veined leaves of monocotyledonous plants allied to the present rushes; they apparently grew on tbe margin of shallow waters, where they were buried in sand or silt. The E. Limmanum of authors probably contains several species. This may also be a dendritic or imitative form, of inorganic material. It stands by the side of eozoon; the one being, in the present state of our knowledge, perhaps the earliest land plant, the other the earliest animal organism.