PREFACE. 
Vll 
Italy, the south of France, and the northern parts of Spain; yet from the well 
established fact of the more southerly position of the isothermal lines on the 
western shores of the Atlantic, its mean annual temperature cannot be compared 
with that of the above mentioned countries, but rather with those lying from 
fifteen to twenty degrees farther north. The result of ten years’ observations at 
New-York, gives one hundred and sixty-five days, or about five months, as the 
mean duration of winter; but in the interior or northern district, many of the 
counties have scarcely a month without frost. This, it will readily be perceived, 
must exercise a great influence upon the number and distribution of its animals; 
for while it has the summer heats of Spain and Italy, the rigor of its winters 
equals those of the northern portions of Europe. From this diversity of climate, 
it results that we have in the State similar classes of animals with those found in 
the northern parts of Europe, and at the same time other families existing chiefly 
in its southern portions. The families Cervidce and Mustelidce may serve as 
examples of the one, while the Vespertilionidce and Muridce will illustrate the 
other. 
Varieties of surface are also well known to be favorable to the multiplication 
of animal species, and in this respect, the State of New-York offers a great diver¬ 
sity ; for although few of its mountains exceed the height of five thousand feet, 
yet from the peculiarity of climate alluded to above, their summits have a tem¬ 
perature much lower than mountains of even higher altitude in corresponding 
parallels in Europe. The surface of New-York is considerably elevated, much 
of it lying on the great Allegany table land. The diversity of surface is, how¬ 
ever, so great, that for the purposes of more intelligible description, we may 
consider it as divided into four principal zoological districts, each sufficiently dis¬ 
tinct in itself, but of course so much blended at the lines of separation as not to 
be contradistinguished. 
1. The Western District , includes that portion of the State which is bounded 
on the west and north by Lakes Erie and Ontario, and on the south by the 
boundary line separating it from the State of Pennsylvania ; and it extends east¬ 
ward^’ until it is lost in the valley of the Mohawk on the north, and the moun¬ 
tainous parts of the Hudson district. A large portion of this district is an elevated 
region, furrowed by valleys running in a north and south direction, supposed 
once to have been the outlets of a great inland ocean, but now the beds of rivers 
which, pursuing opposite courses, discharge themselves on the one hand through 
