Post- Pliocene Deposits of the St. Lawrence. 39 



state of depression in the boulder-clay period, corresponding 

 with what has been deduced from similar appearances in the Old 

 World. " The upheaval of the bed of the glacial sea," says 

 Forbes, " was not sudden but gradual. The phenomena so well 

 described by Prof. Forchhammer in his essays on the Danish 

 drift, indicating a conversion of a muddy sea of some depth into 

 one choked up with sand banks, are, though not universal, equally 

 evident in the British Isles, especially in Ireland and the Isle of 

 Man."* 



We now have in all, exclusive of doubtful forms, 6kty-three 

 species of Marine In vertebrates from the Post-Pliocene or Pleisto- 

 cene clays of the St. Lawrence valley. All, except four or five 

 species belonging to the older or deep-water part of the deposit, 

 are known as living shells of the Arctic or Boreal regions of the 

 Atlantic. About half of the species are fossil in the Pleistocene 

 of Great Britain. A majority of the whole are now living in the 

 Gulf of St. Lawrence and on the neighbouring coasts; and I have 

 reason to believe that the dredging operations carried on by the 

 officers of the Geological Survey in the past summer, will enable 

 us to reeognize all but a few as living Canadian species. In so 

 far, then, as marine life is concerned, the modern period in this 

 country is connected with that of the boulder clay by an un- 

 broken chain of animal existence. These deposits in Lower Ca- 

 nada afford no indications of the terrestrial fauna ; but the remains 

 of Elepli/u Primigenius in beds of similar age in Upper Canada^ 

 show that during the period in question great changes occurred 

 among the animals of the land; and we may hope to find similar 

 evidences in Lower Canada, especially in localities where, as on 

 the Ottawa, the debsris of land-plants and land-shells occur in the 

 marine deposits. 



* Memoirs of Geological Survey. 



f Reports of GeoL Survey; LyelTs Travel 



