MoUusca of Lower Canada, 457 



was that the land in North America, "after it had acquired 

 its present outline of hill and valley, cliff and ravine," was sub- 

 jected to a gradual submergence — and that at a subsequent period 

 it re-emerged from the ocean. Again, it is a well-known fact, that 

 more than half of the marine shells of the northern New England 

 states, and also of the Gulf of the St. Lawrence are common to the 

 seas of northern Europe. This has been held, with much proba- 

 bility, to prove the existence of a land way across the Atlantic 

 since the epoch of the still living animals and plants. 



It should be stated that many American shells, which are 

 not now known to inhabit the European seas, occur fossil in the 

 redcragof Great Britain — this would tend to prove the great anti- 

 quity of the existing fauna. 



If too the Helix labyrinthica (a little snail common in Canada) 

 be, as many of our best naturalists think, identical with a fossil 

 species from the Eocene beds of the Isle of Wight, it is just pos- 

 sible that some of our land shells may prove to be even of still 

 older date. It has been noticed by scientific men in Britain, that 

 these fossil land shells from the Isle of Wight are of a group 

 quite American in character. Neither should we forget the theory 

 that at a period somewhat later geologically than these Eocene 

 beds, the isthmus of Darien, or some portion of it at least, was 

 submerged, and we should take into consideration the supposed 

 consequent alteration of the currents of the gulf stream. It has 

 been suggested that from this cause alone, the climate of Great 

 Britain was then as cold as that of the island of Newfoundland at 

 the present day. 



But here in Canada, our knowledge of facts is much too meagre 

 and unsatisfactory to enable us to generalize either on the distri- 

 bution of plants and animals in British America, or on the con- 

 nection between existing animals and the tertiary formations of 

 this country. The deposits of land and fresh water shells in our 

 lacustrine marls, require to be carefully worked out. and catalo- 

 gues of the species which they contain to be published. In 

 the living land and fresh water mollusca, much is yet to be done ; 

 — the neighbourhood of Lake Superior may yet produce many 

 new fresh water forms, while the vicinity of Toronto, and that 

 part of Canada to the south-west of Lake Erie are, conchologically 

 speaking, almost unknown. The opening up of canals has caused 

 a northward emigration of fresh water shells, and by this means 



several species have been enabled to travel from Ohio into the 

 south-west peninsula of Canada. In my own private collection, 



