1896.] Distribution of Batrachia and Reptilia. 901 
excepting Cryptobranchide. All the families of Salientia 
characteristic of Medicolumbia are present except the Engy- 
stomide. Among reptiles the genus Charina is entirely char- 
acteristic, and Gerrhonotus of the Toltecan and Sonoran faune 
ranges its entire length. It is especially distinguished by 
the absence of the following genera: First, all of the Igua- 
nidæ exclusively characteristic of the Sonoran fauna, there 
remaining only Crotaphytus, Sceloporus, and Phrynosoma, which 
also enter the Texan district of the Austroriparian ; by the 
absence of Heloderma, Ophisaurus and Liolepisma. Amon 
snakes, by the absence of true water snakes (genus Natrix), 
and the small burrowing Natricine, of Opisthoglyph forms, 
and of poisonous snakes of the genera Elaps and Systrurus. 
No genus but Charina can be cited as of universal distribution, 
which is not at the same time found in some other subregion ; 
but several genera occur in one or the other of its districts 
which do not occur elsewhere. Similarly no genus of birds or 
mammals can be exclusively assigned to its entire area; but 
Chamea of the former class and Haplodontia of the latter are 
restricted to particular portions of it. 
The Toltecan subregion is characterized by the genera it lacks 
as well as those which it possesses. Thus, it lacks all the 
genera of Sauria above cited as characteristic of the Sonoran 
subregion, including those enumerated as passing over into the 
Austroriparian ecept Phrynosoma. It also lacks the following 
genera of snakes which are found in the Sonoran: 
Lichanura, Zamenis, 
Pityophis, Phyllorhynchus. 
Ophibolus, 
Chilomeniscus, 
From the Austroriparian subregion it differs in the lack of 
all the numerous genera of Fishes and Batrachia Urodela, 
which characterize it, excepting only Spelerpes. It lacks also 
the following genera of snakes: Cyclophis, Virginia, Haldea and 
Carphophiops ; and Natrix is very sparsely if at all represented, 
In its positive characters the Toltecan subregion combines 
certain forms of both the Sonoran and Austroriparian subre- 
