The question of the general relation of an organism like Eozoon to creatures known to us in the modern seas may be answered in either of two ways:--(1) Functionally or in relation to the position of such an animal in nature: or (2) Zoologically, or with reference to its affinities to other animals. With reference to the first consideration, the answer is plain. The geological function of Eozoon was that of a collector of calcareous matter from the surrounding waters, then probably very rich in calcium carbonate, and its role was the same with that of the Stromatoporæ and calcareous Sponges, smaller Foraminifera and Corals in latter times. The answer to the second aspect of the question is less easy. An ordinary observer would at once place Eozoon with the Stromatoporidæ or Layer-corals, which fill or even constitute whole beds of limestone in the Cambro-Silurian, Silurian and Devonian Periods. While, however, Eozoon has been claimed on the highest authority for the Rhizopods, the Stromatoporæ and their allies have been regarded as Sponges, or more recently as Hydroids allied to the Hydractiniæ and Millepores.[53] I confess that I am not satisfied with these interpretations. I have in my collections large numbers of encrusting spinous forms, usually called Stromatoporæ, but which I have long set aside as probably Hydractiniæ. There are other forms with large vertical tubes which I have regarded as corals, but some Stromatoporæ seem to be different from either, and I am still disposed to regard many of them as Protozoa. Bearing in mind, however, that the Silurian is as remote from the Laurentian on the one hand as from the Tertiary on the other, we might be prepared to expect that if the Layer-corals of the Silurian are divisible into different groups, somewhat widely separated, and we have in the lower Palæozoic the peculiar type of Cryptozoon, we may be prepared to expect in the Laurentian much more generalized forms, less susceptible of classification in our modern systems. If, therefore, Eozoon were accessible to us in a living state, I should not be surprised to find that--while perhaps more akin to the calcareous-shelled Rhizopods than to any other modern group--it may have presented points of resemblance to Sponges or even to Hydroids, in its skeleton and mode of growth, and even in the arrangement of its soft parts. [Footnote 53: See Nicholson and Murie's able memoirs, Publications of Pal. Soc, 1885.] Taking this view of its nature and relations, the genus and the Laurentian species may be characterized as follows:-- _Genus_ Eozoon, _Dawson_. Foraminiferal skeletons, with irregular and often confluent cells, arranged in concentric and horizontal laminæ, or sometimes piled in an acervuline manner. Septal orifices irregularly disposed. Proper wall finely tubulated. Intermediate skeleton with branching canals. Eozoon Canadense, _Dawson_.