150 THE DAWN OF LIFE. 



already tenanted by many kinds of crustaceans and 

 shell-fishes^ which have been collected and described 

 by palseontologists in Bohemia^ Scandinavia^ Wales, 

 and North America ; * curiously enough, however, the 

 rocks of this age are not so rich in Foraminifera as 

 those of some succeeding periods. Had this primitive 

 type played out its part in the Eozoic and exhausted 

 its energies, and did it remain in abeyance in the 

 Primordial age to resume its activity in the succeeding 

 times ? It is not necessary to believe this. The 

 geologist is familiar with the fact, that in one forma- 

 tion he may have before him chiefly oceanic and deep- 

 sea deposits, and in another those of the shallower 

 waters, and that alternations of these may, in the same 

 age or immediately succeeding ages, present very dif- 

 ferent groups of fossils. Now the rocks and fossils of 

 the Laurentian seem to be oceanic in character, while 

 the Huronian and early Primordial rocks evidence 

 great disturbances, and much coarse and muddy sedi- 

 ment, such as that found in shallows or near the land. 

 They abound in coarse conglomerates, sandstones and 

 thick beds of slate or shale, but are not rich in limestones, 

 which do not in the parts of the world yet explored 

 regain their importance till the succeeding Siluro- 

 Cambrian age. No doubt there were, in the Primor- 

 dial, deep-sea areas swarming with Foraminifera, the 

 successors of Eozoon; but these are as yet unknown 

 or little known, and our known Primordial fauna is 

 chiefly that of the shallows. Enlarged knowledge may 

 * Barrande, Angelin, Hicks, Hall, Billings, etc. 



