1012 The American Naturalist. : [December, 
The total number of species of the Floridan subregion is as 
follows: 
Peculiar species, . ; : 7 : 15 
Species common to the Ocmulgian district, 1 
Species common to the Louisianian district,. . . 40 
Species common to the West Indian region, 3 
Little known species, : 2 
61 
VI. THE SONORAN SUBREGION. 
This subregion presents several natural divisions, as follows : 
I. The Lower Californian district, including only the region 
at the extremity of the peninsula of Lower California ; II. The 
Chihuahuan district, embracing the State of Sonora, Mexico, 
the northern part of the Mexican Plateau, Arizona south of 
the San Francisco Mountains, most of the peninsula of Lower 
California, and most of New Mexico; III. The Basin district, 
embracing the Great Basin of Utah and Oregon, to Vernon, 
British Columbia; and IV. The Central district, which in- 
cludes the high plains east of the Rocky Mountains, from 
Texas northward, excepting the river bottoms which cross It 
from west to east. This great subregion is bound together by 
the general distribution of numerous genera; but I do not 
know a single species which covers its entire area which is not 
found elsewhere. These define the districts. na 
The Lower Californian district is defined by the following 
fourteen species, which are restricted to it: = 
Hyla curta Cope. Zamenis aurigulus Cope. 
Ctenosaura hemilopha Cope. Phyllorhynchus decurtatus 
Uta thalassina Cope. ope. 
Uta nigricauda Cope. Pityophis vertebralis Blv. 
Phyliodactylus unctus Cope. Chilomeniscus stramineus 
Cnemidophorus maximus Cope. 
Cope. 3 Tantilla planiceps Bly. 
Euchirotes diporus Cope. Orotalus enyo Cope. 
Lichanura trivirgata Cope. 
