FORAMIN1FERA AND KADIOLARIA. 101 



eral layers which are most numerous towards the centre of the disk, and 

 thin-away gradually towards its margin. The disposition and connec- 

 tions of the chamberlets of the median layer in Orbitoides seem to corre- 

 spond very closely with those which have been already described as pre- 

 vailing in Cyclodypeus; the most satisfactory indications to this effect 

 being furnished by the siliceous ' internal casts ' to be met with in cer- 

 tain Green Sands, which afford a model of the sarco-de-body of the ani- 

 mal. In such a fragment (Fig. 342) we recognize the chamberlets of 

 three successive zones, a, a', a", each of which seems normally to com- 

 municate by one or two passages with the chamberlets of the zone inter- 

 nal and external to its own; whilst between the chamberlets of the same 

 .zone there seems to be no direct connection. They are brought into rela- 



Fro. 343. 



Vertical Section of Eozoon Canadense> showing alternation of Calcareous (light) and Serpentin- 

 ous (dark) lamellae. 



tion, however, by means of annular canals, which seem to represent the 

 spiral canals of the Nummulite, and of which the ' internal casts ' are 

 seen at b b, V b', V 9 I". 



493. A most remarkable Fossil, referable to the Foraminiferal type, 

 has been recently discovered in strata much older than the very earliest 

 that were previously known to contain Organic remains; and the deter- 

 mination of its real character may be regarded as one of the most inter- 

 esting results of Microscopic research. This fossil, which has received 

 the name Eozoon Canadense (Fig. 343), is found in beds of Serpentine 

 Limestone that occur near the base of the Laurentian formation 1 of 



1 This Laurentian formation was first identified as a regular series of stratified 

 rocks, underlying the equivalents not merely of the Silurian, but also of the 

 Upper and Lower Cambrian systems of this country, by Sir William Logan, the 

 former able Director of the Geological Survey of Canada. 



