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 he considered an 
altogether natural, sub-region. 
We will now give an outline of the most important zoological 
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. 
I. 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 Phyllostomkke and Noctilionidse, 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 (Phyllostomidee), one 
species in California ; Antrozous (Vespertilionidse), one species 
on the West Coast; Urotrichus (Talpidse) one species in British 
Columbia ; sub-genus Neserex (Soricid<e), one species in Oregon ; 
Bassaris (Procyonidae), California ; Enhydra (Mustelidse), Pacific 
Coast; Morunga (Phocidse), California; Haploodon (Haploodon- 
tidse) 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, Bidelphys, 
Sciuropterns, Tamias , Spermophilus , Bipodomys, Perognathus , 
Jaculus. 
Birds . — Few genera of birds are quite peculiar to this sub- 
region, since most of the Western forms extendjnto the central 
district, yet it has a few. Olaucidnm, a genus of Owls, is confined 
