Castoroides Ohioensis. 389 
ridges of drift only raised above the level of the waters, giving 
a vastly greater proportion of this kind of surface than at pre- 
sent. Thus far the bones of the mastodon and elephant hav® 
all been found at a higher elevation than the relic under con- 
sideration, and this is precisely what we should expect, with 
the condition of surface we have described. The animal in 
question doubtless found the extensive marshes, with wooded 
margins and intervening higher grounds, well adapted to its 
wants and mode of life. That its remains have been so rarely 
met with, may be explained from the fact, that very few ex- 
tensive excavations have been made in situations likely to 
contain them ; while the smaller and more elevated marshes, 
where the bones of the mastodon have been found, are more 
accessible and oftener excavated. Therefore, from all we know 
at present, this animal may have abounded on the marshy 
borders of the former Lake Ontario, when the now fertile re- 
gions of Oswego, Wayne, Monroe, Orleans and Niagara coun- 
ties, as well as the corresponding parts of Canada were mostly 
covered by water and marshes. 
So far as the general features are concerned, and the rela- 
tive age of the deposition, there cannot remain a doubt ; and 
although as yet no other bones have been found with this cra- 
nium, we feel justified in referring its period to that of the 
Sreat mastodon and other animals of our country, whose re- 
Mains have been found in similar situations. The relative 
level of the surface of the country, at this place, varies very 
ittle from that of Rochester, where. the bones of a mastodon 
Vere found some years since.' The bones found at Genesee, 
Many years since, were proved to have occurred in the marl 
of a Swamp, over which was deposited a layer of peaty mat- 
_ r^ All the other situations, where similar bones have been 
; correspond to this one in general characters, with per- 
the partial exception of the tooth of a mastodon found 
: "€ Geological Report of the Fourth District, N. Y., 1843, p. 363. L yell. 
See as above. iut 
