252 THE FOEAMINIFEEA 



are comparatively rare in the older rocks, we may 

 reasonably infer that the types of Protozoa, which 

 very probably existed in earliest times and in pro- 

 digious abundance, were chiefly represented by those 

 forms which did not possess an investment of hard 

 material, but consisted merely of sarcode, or perhaps 

 were covered by a thin chitinous investment. This 

 conjecture, however, will require proof which i^rima 

 facie will be next to impossible to obtain, for the 

 chitinous forms are practically unknown as fossils. 



It appears by recent researches to be pretty 

 conclusively proved that the w^hilom sensational 

 Eozoon Canadense of the Laurentian limestone rocks 

 of Canada and elsewhere is not a gigantic foramini- 

 fer. Whether it be a purely mineral structure or a 

 mineralised organism of a larger type of growth, such 

 as a hydrozoan, remains to be seen ; it will not be 

 necessary to dwell further upon it here. 



Some exceedingly minute bodies resembling Fora- 

 minifera in their general form have been described 

 by Cayeux from the Pre-Cambrian of Brittany, where 

 they occur in quartzites and pthanites. They are, 

 however, of such small dimensions, the largest of 

 their segments having a diameter of only 05^00^ inch, 

 that their relation to Foraminifera may be con- 

 sidered somewhat doubtful. 



Four noteworthy occurrences of Foraminifera 

 have been recorded from Cambrian strata. Ehren- 

 berg, in 1858, figured various glauconitic casts 

 of Foraminifera from the so-called ' Silurian clay ' 

 near St. Petersburg, which apparently belong to 



