74 THE DAWN OF LIFE. 



forms of a different group in so far as shell-structure is 

 concerned. It may thus be regarded as a composite 

 type, combining peculiarities now observed in two 

 groups, or it may be regarded as a representative in the 

 Nummuline series of Polytrema and Tinoporus in the 

 Eotaline series. At the time when Dr. Carpenter stated 

 these affinities, it might be objected that Foraminifera 

 of these families are in the main found in the Modern 

 and Tertiary periods. Dr. Carpenter has since shown 

 that the curious oval Foraminifer called Fusulina, found 

 in the coal formation, is in like manner allied to both 

 Nummulites and Rotalines ; and still more recently 

 Mr. Brady has discovered a true Nummulite in the 

 Lower Carboniferous of Belgium. This group being 

 now fairly brought down to the Palaeozoic, we may hope 

 finally to trace it back to the Primordial, and thus to 

 bring it still nearer to Eozoon in time. 



Though Eozoon was probably not the only animal of 

 the Lau-rentian seas, yet it was in all likelihood the 

 most conspicuous and important as a collector of cal- 

 careous matter, filling the same place afterwards 

 occupied by the reef-building corals. Though pro- 

 bably less efficient than these as a constructor of solid 

 limestones, from its less permanent and continuous 

 growth, it formed wide floors and patches on the sea- 

 bottom, and when these were broken up vast quantities 

 of limestone were formed from their debris. It must 

 also be borne in mind that Eozoon was not everywhere 

 infiltrated with serpentine or other silicious minerals ; 

 quantities of its substance were merely filled with car- 



