HISTORICAL PALEONTOLOGY. 



CHAPTER XLVL 

 LAURENTIAN AND CAMBRIAN PERIODS. 



IN this portion of the work it will be endeavoured very briefly 

 to give a view of the forms of life which characterised each of 

 the great geological periods. The subject of the fossils which 

 characterise each particular stratum or group of strata in the 

 earth's crust is one far too vast to be grappled with here, and 

 can only be properly considered in a special treatise. All that 

 will be attempted here is to give a short synopsis of the de- 

 posits of each successive era, followed by a general account of 

 the " life " of the period in which those deposits were laid 

 down. Such an account may be advantageously prefaced by 

 a tabular view of the more important fossiliferous deposits, 

 commencing with the most ancient. 



TABULAR VIEW OF FOSSILIFEROUS STRATA. 



I. PALAEOZOIC OR PRIMARY EPOCH. 

 ( Terrains Paleozo'iques. ) 



i. LAURENTIAN. 



a. Lower Laurentian. British Wanting. Foreign Great series of 



metamorphic rocks in Canada, gneiss, mica-schist, quartzite, and 

 limestones, with a total thickness of about 20,000 feet. 



b. Upper Laurentian. British Fundamental Gneiss of the Hebrides (?) ; 



Hypersthene Rocks of the Isle of Skye (?). Foreign Labrador Series 

 of Canada, having a thickness of 10,000 feet, and resting unconform- 

 ably upon the Lower Laurentian. 



2. HURONIAN. 



British Wanting (?). Foreign About 18,000 feet of metamorphic rocks 

 resting unconformably upon the Laurentian series of Canada. Per- 

 haps the equivalent of the Lower Cambrian of other regions. 



