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CHAP. XV.] THE NEARCTIC REGION. 127
forms, while many of those peculiar to the south are absent ; so
that it is a very convenient, if it should not be considered an
altogether natural, sub-region.
We will now give an outline of the most important ;50ological
features of each of these divisions, taking them in the order
in which they are arranged in the Fourth Part of this work,
California comes first, as it has some tropical forms not found
elsewhere, and thus forms a transition from the Neotropical
region.
/. The Western or Californian Sub-region.
This small district possesses a fruitful soil and a highly
favourable climate, and is, in proportion to its extent, perhaps
the richest portion of the continent, both zoologically and botan-
ically. Its winters are far milder than those of the Eastern
States in corresponding latitudes ;
and this, perhaps, has enabled
it to support several tropical forms which give a special character
to its fauna. It is here only, in the whole region, that bats of
the families Phyllostomidae and Noctilionidae, and a serpent of
the tropical family, Pythonidse, are found, as well as several
Neotropical forms of birds and reptiles.
Mammalia.—The following genera are not found in any other
part of the Nearctic region, Macrotus (Phyllostomidce), one
species in California ; Antrozous (Vespertilionidse), one species
on the "West Coast ; Urotrichus (Talpidas) one species in British
Columbia; sub-genus iVcsorea; (Soricidae), one species in" Oregon ;
Bassaris (Procyonidee), California ; Enhydra (Mustelidse), Pacific
Coast; Morunga (Phocidae), California; ^apZoo6?07i (Haploodon-
tidfe) a rat-like animal, allied to the beavers and marmots, and
constituting a peculiar family found only in California and
British Columbia. The following characteristic Nearctic forms
also extend into this sub-region :
—
Taxidea, Procyon, Didelphys,
Sciuropterus, Tamias, Spermophilus, Dipodomys, Perognathus,
Jaculus.
Birds.—Pew genera of birds are quite peculiar to this sub-
region, since most of the Western forms extend into the central
district, yet it has a few. Olaucidium a genus of Owls, is confined