1865.] DAWSON— STRUCTURE OP EOZOoN 109 



as to their vegetable origin if they were found in fossiliferous 

 limestones. 



5. A specimen of impure limestone from Madoc, in the collection 

 of the Canadian Geological Survey, which seems from its structure 

 to have been a finely laminated sediment, shows perforations of 

 various sizes, somewhat scalloped at the sides, and filled with grains 

 of rounded siliceous sand. In my own collection there are specimens 

 of micaceous slate from the same region, with indications on their 

 weathered surfaces of similar rounded perforations, having the 

 aspect of ScolithuSj or of worm-burrows, 



I would observe, in conclusion, that the observations detailed in 

 this paper must be regarded as merely an introduction to a most 

 interesting and promising field of research. The specimens to 

 which I had access were for the most part collected by the explorers 

 of the Survey merely as rocks, and without any view to the possible 

 existence of fossils in them. It may be hoped, therefore, that 

 other and more perfect specimens may reward a careful search in 

 the localities from which those now described have been obtained. 



Further, though the abundance and wide distribution of Eozoon, 

 and the important part it seems to have acted in the accumulation 

 of limestone, indicate that it was one of the most prevalent forms 

 of animal existence in the seas of the Laurentian period, the 

 non-existence of other organic beings is not implied. On the 

 contrary, independently of the indications afforded by the 

 limestones themselves, it is evident that in order to the existence 

 and growth of these large llhizopods, the waters must have 

 swarmed with more minute animal or vegetable organisms on which 

 they could subsist. On the other hand, though this is a less certain 

 inference, the dense calcareous skeleton of Eozoon may indicate 

 that it also was liable to the attacks of animal enemies. It is also 

 possible that the growth of Eozoon, or the deposition of the 

 serpentine and pyroxene in which its remains have been preserved, 

 or both, may have been connected with certain oceanic depths and 

 conditions, and that we have as yet revealed to us the life of only 

 certain stations in the Laurentian seas. Whatever conjectures we 

 may form on these more problematic points, the observations above 

 detailed appear to establish the following conclusions : — First, that 

 in the Laurentian period, as in subsequent geological epochs, the 

 llhizopods were important agents in the accumulation of beds of 

 limestone ; and secondly, that in this early period these low forms 

 of animal life attained to a development, in point of magnitude 



