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 



