Proceedings of the British Association. 357 
which are common to both North America and Europe ; though 
possibly a closer acquaintance with some which are at present con- 
sidered identical, may enable us to establish some distinction between 
them. The generic forms of North America are the same as those 
of Europe, excepting in a very few cases, which belong to.the South 
American group. A few of the more northern forms also cross the 
Isthmus of Darien to the south.—In the family of Plantigrada, two 
of the four bears of North America are undoubtedly peculiar to the 
New World; and one of these is the most northerly quadruped it 
contains. The American Glutton, or Wolverine according to Cu- 
vier, is identical with that of the Old World. Among the Digiti- 
grada, the range of the Mustelz is limited southwards to the north- 
ern or middle district of the United States. Whether any of the 
American and European species of this genus be really identical, is 
involved in great uncertainty. Of the three otters of North Amer- 
ica, One appears to be identical with that of Europe; and another, 
if correctly identified as the Lutra Brasiliensis, has a most exten- 
sive range, from the Arctic Sea through great part of South Amer- 
ica. Eight species of the genus Canis are found in North America ; 
but there is great difficulty in distinguishing the species, and in iden- 
tifying them with any of those of Europe. The domestic dog 
breeds with the wolf and fox, and their offspring is prolific. Eight 
species of the genus Felis were mentioned by Dr. Richardson, three 
of which extend from South America into the south western territo- 
ries of the United States ; and some of the others are still doubtful 
as North American species. The nine species of Amphibia found 
~ in North America, are mostly common to the northern seas of the 
Old and New Worlds ; the genus Otaria alone being confined to the 
North Pacific; and even these range to the Asiatic coast. The 
specific identity of some of the seals is involved in very great doubt. 
In the order Rodentia, there have been between seventy and eighty 
species discovered ; and here North America surpasses every quar- 
ter of the globe in the abundance and variety of form which 
animals assume. The squirrels are not yet satisfactorily determined. 
The marmots are numerous, except in the subgenus Spermophilus. 
There is only one which may possibly be common to the New and 
Old World. There is only one of the restricted genus Mus, which © 
is unequivocally indigenous to North America; and this closely re- 
sembles the European M. sylvestris. Other species have been in- 
troduced from the opposite side of the Atlantic. 
