MOLLUSCA OF LOWER CANADA. 55 



while the paucity of species of the large families of Umbelliferse 

 and Cruciferse is quite noticeable in Lower Canada. 



The line of demarcation between the Canadian part of Dr. 

 Hooker's sub-arctic region, and the outlier, so to speak, of the 

 Atlantic region, in Canada, cannot be accurately defined. No 

 isothermal line will suffice, for the simple reason that since the 

 creation of the still existing fauna and flora, such physical changes 

 have been effected, that the isothermals during the newer tertiary 

 period must have been constantly varying. To sum up this part of 

 our subject, — we have, as it seems to me, in this vast province, 

 fragments, so to speak, of three natural-history regions. Canada, 

 on the whole, as defined on the map, has not a race of 

 animals, or a group of plants which are so special and peculiar 

 to it as to constitute a good natural-history province. As I have 

 endeavoured to shew, the southwest peninsula of Upper Canada is 

 an outlier of the western region ; and the remainder of Canada is 

 partly of a sub-arctic type, and partly, so far as its zoology and botany 

 are concerned, has affinities with the northern Atlantic states. 

 With one remark I shall close this part of our subject. 

 Prof. Asa Gray has shown us that the plants of eastern North 

 America bear a greater resemblance to those of Japan, than 

 those inhabiting the tract of land between the Rocky Mountains 

 and the Pacific. At a meeting of the Natural Historv Society of 

 Boston, Dr. Gould exhibited a marine bivalve shell (a species of 

 Leda) also from Japan, which he considered identical with a living 

 Massachusetts species. It would be interesting to the naturalist 

 to know if the same similarity obtaius between the mollusca, &c, 

 of the two countries, as the relations of their flora would seem to 

 warrant. 



But in order to be enabled to speculate with any degree of ac- 

 curacy on the rationale of the present geographical distribution of 

 animals and plants, we must also carefully glean what little evid- 

 ence we may from the geologic record. Since the creation of at least 

 some of the animals and plants which still people Europe and North 

 America, mighty physical changes on the earth's surface have been 

 apparently effected, to the consideration of which, as bearing direct- 

 ly on my subject, I would call some attention. Dr. Dawson has 

 carefully catalogued the drift fossils from Beauport, the neigh- 

 borhood of Montreal, Green's Creek on the Ottawa, and part of 

 Maine. To match these we want complete and accurate lists of the 

 marine invertebrata of the Gulf of the St. Lawrence, and carefully 



