Geological Society. 201 



almost obsolete, there being only faint indications of them on the 

 sides of the body. 



The most important distinction, however, exists in the teeth, the 

 present specimen possessing altogether' four more molars than the 

 one brought before the notice of the Society on a previous occasion. 

 The entire number of teeth is 52, (26 in each jaw), and the 5 posterior 

 molars are placed closely together, differing in that respect from 

 those of the previously examined specimen. 



The animal was brought from Van Diemen's Land, and others 

 similar to it were observed scratching at the roots of trees, and 

 feeding upon the insects which are generally abundant in such situ- 

 ations. Their favourite haunts are stated to be the localities in 

 which the Port Jackson willow is most plentiful. 



Mr. Waterhouse remarked that although the differences between 

 the two animals were considerable, yet he did not consider the di- 

 stinctions such as to justify his characterizing the one then before 

 the Meeting as a second species. 



GEOLOGICAL SOCIETY. 



March 22. — A paper " On the Ancient State of the North American 

 Continent;" by Thomas Roy, Esq., Civil Engineer, Toronto, Upper 

 Canada, and communicated by Charles Lyell, Esq., F.G.S., was read 

 in part. 



April 5. — The reading of Mr. Roy's paper was concluded. 



The author having in the course of his professional duties, disco- 

 vered in the lake district of Upper Canada terraces or level ridges 

 which agreed in elevation at considerable horizontal distances, he 

 was induced to extend his inquiries and to ascertain how far similar 

 phaenomena have been observed in other parts of North America, — 

 what may have been the probable extent of the lake or sea by which 

 the ridges were formed, — and by what operations the waters were 

 drained off, leaving only the present detached Canadian lakes. 



With a view to ascertain the probable extent of the sea, Mr. Roy 

 traced upwards from Lake Ontario the successive ridges or terraces*, 

 and ascertained that their greatest height was 762 feet above the 

 lake, or 996 feet above the ocean j he therefore assumed, that the 

 boundary of the ancient sea must have had an elevation of at least 

 1000 feet, and in consequence, that it must have been formed on the 

 west by the rocks and mountains ranging from the table-land of 

 Mexico to the parallel of 47° of latitude j on the north by the barrier 

 which separates the head-waters of the lakes from those of the Arctic 

 rivers, and extending to CapeTourmente below Quebec ; on the east 

 by the hills stretching through the United States to the GuU of 

 Mexico ; and on the south by a mountain ridge which has been de- 

 stroyed. The area thus circumscribed is calculated to be 960,000 

 square miles. 



The chief geological feature connected with Mr. Roy's observations 



* These parallel ridges were exhibited on a section extending obliquely 

 from the mouth of the Niagara to the south of Lake Ontario, and over the 

 ridge north of that lake, to Lake Simcoe. 



Third Series. Vol. 1 1. No. 66. Aug. 1837. 2 D 



