326 Royal Society : — 



of the Laurentian series of rocks in Canada. The geological position 

 of this fossil (almost 40,000 feet beneath the base of the Silurian 

 system) is scarcely more remarkable than its zoological relations ; for 

 there is found in it the evidence of a most extraordinary development 

 of that Rhizopod type of animal life which at the present time pre- 

 sents itself only in forms of comparative insignificance — a development 

 which enabled it to separate carbonate of lime from the ocean-waters 

 in quantity sufficient to produce masses rivalling in bulk and solidity 

 those of the stony corals of later epochs, and thus to furnish (as 

 there seems good reason to believe) the materials of those calcareous 

 strata which occur in the higher parts of the Laurentian series. 



Although a detailed account of this discovery, including the results 

 of the microscopic examinations into the structure of the fossil which 

 have been made by Dr. Dawson and myself, has been already com- 

 municated to the Geological Society by Sir William E. Logan, I 

 venture to beHeve that the Fellows of the Royal Society may be glad 

 to be more directly made acquainted with my view of its relations to 

 the types of Foraminifera which I have already described in the Phi- 

 losophical Transactions. 



The massive skeletons of the Rhizopod to which the name Eozoon 

 Canadense has been given, seem to have extended themselves over the 

 surface of submarine rocks, their base frequently reaching a diameter 

 of 1 2 inches, and their thickness being usually from 4 to 6 inches. 

 A vertical section of one of these masses exhibits a more or less regular 

 alternation of calcareous and siliceous layers, these being most distinct 

 in the basal portion. The specimens which the kindness of Sir 

 William E. Logan has given me the opportunity of examining are 

 composed of carbonate of lime alternating with serpentine — the cal- 

 careous layers being formed by the original skeleton of the animal, 

 whilst the serpentine has filled up the cavities once occupied by its 

 sarcode-body. In other specimens the carbonate of lime is replaced 

 by dolomite, and the serpentine by pyroxene, Loganite, or some 

 other mineral of which silex is a principal constituent. The regular 

 alternation of calcareous and siliceous layers which is characteristic 

 of the basal portion of these masses, frequently gives place in the 

 more superficial parts to a mutual interpenetration of these minerals, 

 the green spots of the serpentine being scattered over the surface of 

 the section, instead of being collected in continuous bands, so as to 

 give it a granular instead of a striated aspect. This difference we 

 shall find to depend upon a departure from the typical plan of growth, 

 which often occurs (as in other Foraminifera) in the later stages — the 

 minute chambers being no longer arranged in continuous tiers, but 

 being piled together irregularly, in a manner resembling that in which 

 the cancelli are disposed at the extremities of a long bone. 



The minute structure of this organism may be determined by the 

 microscopic examination either of thin transparent sections, or of 

 portions which have been submitted to the action of dilute acid, so 

 as to remove the calcareous shell, leaving only the siliceous casts 

 of the chambers and other cavities originally occupied by the sub- 

 stance of the animal. Each of these modes of examination, as I have 



