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coast of America, such as are now well known to exist 

 between species of animals of the American and European 

 continents, which were formerly thought to be identical. 

 Many species of shells of Carolina and the Gulf of Mexico 

 have heretofore been regarded as the same as species 

 existing in California. Their general characters are alike, 

 but on being compared side by side, they are found to 

 differ in their details. Dr. Gould exhibited to the Society 

 a piece of bark covered with Mytili, of a new species from 

 Monterey. 



Mr. Desor made some remarks concerning the origin of 

 some of the elements of the so-called Tertiary or drift of 

 Lake Superior. 



He stated, that all along the shores of this Lake and in 

 the drift around it there are found pebbles of white lime- 

 stone and fossil corals. It has been a question among 

 geologists from what source they have been derived. 

 Their characters would seem to refer them to the Niagara 

 limestone. No deposit north of their present position has 

 been known to which they could be traced in accordance 

 with tlie general law of the course of the drift from north 

 to south. Mr. Desor was inclined to refer them to the 

 valley of the Mackenzie, where the Niagara limestone is 

 known to exist. Recently, Mr. Logan, the head of the 

 Geological Commission of Canada, had made an excursion 

 to Lake Temiscomeng, fifty miles north of Georgian Bay, 

 where he had discovered an extensive formation of Niagara 

 limestone ; and from the report of voyageurs, the country to 

 the north as far as Hudson's Bay is an immense basin of 

 Silurian formation, the counterpart to the great basin of the 

 Western States, so that the granite north of Lake Supe- 

 rior is to be regarded rather as constituting an anticlinal 

 axis interrupting this whole formation than a proper barrier 

 to the southern basin. The fossils spoken of probably came 

 from the region north of the Lake Superior granite. 



