THE PRIMORDIAL, OR CAMBRIAN AGE. 37 



characteristic features of tlio older Cambrian in both 

 hemispheres. Such conditions, undoubtedly not fa- 

 vourable to life, seem to have prevailed, and extended 

 their influence very widely, so that the sediments of 

 this period are among the most barren in fossils of 

 any in the crust of the earth. If any quiet undis- 

 turbed spots existed in which the Lower Laurentian 

 life could be continued and extended in preparation 

 for the next period, we have yet discovered few of 

 them. The experience of other geological periods 

 would, however, entitle us to look for such oases in 

 the Lower Cambrian desert, and to expect to find 

 there some connecting links between the life of the 

 Bozoic and the very dissimilar fauna of the Primor- 

 dial. 



The western hemisphere, where the Laurentian is 

 so well represented, is especially unproductive in 

 fossils of the immediately succeeding period. The 

 only known exception is the occurrence of Eozoon 

 and of apparent casts of worm-burrows in rocks at 

 Madoc in Canada, overlying the Laurentian, and be- 

 lieved to be of Huronian age, and certain obscure 

 fossils of uncertain affinities, recently detected by Mr. 

 Billings, in rocks supposed to be of this age, in New- 

 foundland. Here, however, the European series comes 

 in to give us some small help. Gumbel has described 

 in Bavaria a great series of gneissic rocks correspond- 

 ing to the Laurentian, or at least to the lower part of 

 it ; above these are what he calls the Hercynian mica- 

 slate and primitive clay- slate, in the latter of which 



