10 BULLETIN OF THE NATURAL HLSTORY SOCIETY. 



the harbour, and the Loch Lomond and Quaco Hills on the 

 other, testify to the activity of volcanic vents near St. John 

 in those early times. And it has recently been discovered 

 that a similar substratum of volcanic deposits underlies the 

 Oambrian rocks in Pennsylvania and southward. 



In nearly all countries where we know of the presence of 

 Cambrian rocks, this time of volcanic activity was followed 

 by the appearance of a warm-water fauna, as though the 

 volcanoes themselves, either by the heat they liberated, or by 

 their effect on atmospheric phenomena, had sensibly influenced 

 the temperature of the sea. This warm-water fauna (or warm 

 and shallow-water fauna) is found wide-spread along the base 

 of the Rocky Mountains, has recently been discovered in the 

 southern Appalachian range, and existed also in the St. 

 Lawrence valley and near St. Joha. 



On the other side of the Atlantic it has been found in 

 the west of England, in the north of Scotland and in Norway 

 and Sweden. 



In these latter countries it was superseded by the Para- 

 doxides fauna; whose origin we know not, except that as it 

 was borne from Europe to our shores, its fountain head 

 would seem to have been the Arctic regions of the Old World. 

 This is the best known fauna of the St. John group ; it came 

 to us on the cold current from northern Europe, but so far as 

 we know was never able to pass the mountain barrier of east- 

 ern North America, or establish itself in the interior of the 

 continent. 



After spreading itself along these Atlantic shores, changes 

 supervened, which brought in a new fauna in the colder seas. 

 The cause of this change is unknown, but it was accompanied 

 by a rising of the land here, as well as in Wales and France. 

 When the land sank again, we find that the northern seas 

 were in the possession of a new group of animals, the gigantic 

 Paradoxides had disappeared, and the Oleni, little crustaceans, 

 many of them not larger than a filbert, had taken their 

 place. 



