No. 5.] NATURAL HISTORY SOCIETY. 279 



Nor is tlie fauna so very meagre as might be supposed. My 

 own collections from Northumberland Strait include about 50 

 species of mollusks, and some not possessed by me have been 

 found by Mr. Whiteaves, Some of these, it is true, are northern 

 forms, but the majority are of New England species. 



The causes of this exceptional condition of things in the Acadian 

 Bay carry us far back in geological time. The area now consti- 

 tuting the Gulf of St. Lawrence seems to have been exempt from 

 the great movements of plication and elevation which produced 

 the hilly and metamorphic ridges of the east coast of America. 

 These all die out and disappear as they approach its southern 

 shore. The tranquil and gradual passage from the Lower to the 

 Upper Silurian ascertained by Billings in the rocks of xVnticosti, 

 and unique in North x\merica, furnishes an excellent illustration 

 of this. In the Carboniferous period the Gulf of St. Lawrence 

 was a sea area as now, but with wider limits, and at that time 

 its southei 1) part was much filled up with sandy and muddy 

 detritus, -Awd its margins were invaded by beds and dykes of 

 trappea;» rocks. In the Triassic age the red sandstones of that 

 period were extensively deposited in the Acadian Bay, and in 

 part have been raised out of the water in Prince Edward Island, 

 while the whole Bay was shallowed and in part cut off from the 

 remainder of the GuH by the elevation of ridges of Lower Car- 

 boniferous rocks across its mouth. In the Post-pliocene period, 

 that which immediately precedes our own modern age. as I have 

 elsewhere shown, -'^ there was s>reat subsidence of this reoion, 

 accompanied by a cold climate, and boulders of Laurentian 

 rocks were drifted from Labrador and deposited on Prince 

 Edward Island and Nova Scotia, while the southern currents 

 flowing up what is now the Bay of Fundy, drifted stones from the 

 hills of New BrunsAvick to Prince Edward Island. At this time 

 the Acadian Bay enjoyed no exemption from the general cold, 

 for at Campbelltown, in Prince Edward Island, and at Bathurst 

 in New Brunswick, we find in the clays and gravels the northern 

 shells generally characteristic of the Post-pliocene ; though 

 perhaps the lists given by Mr. Matthew for St. John and by 

 Mr. Paisley for the vicinity of Bathurst, may be held to shew 

 some slight mitigation of the Arctic conditions as compared 

 with the typical deposits in the St. Lawrence valley. Since 



* Notes on Post-pliuccnc uf Canada, Canadian Naturalist^ 1872 



