1210 REPORT OF NATIONAL MUSEUM, 1898. 



The following genera of reptiles are peculiar to it: 



Uta. Anota. 



Uma. Lichanura. 



Sauromalus. Phyllorhynchus. 



Callisaurns. Chio n actis. 



Dipsosavrxfi. Chilomeniscn.s. 



It sliaies the following genera with the Toltecan subregion and the 

 Central American subregion of the Neotropical Realm only: 



Gtenosaura. 



EuhlephartH (also in the Indian region). 



rhyllodactyhifi (also in the Columbian Neotropical). 



HclixJerma. 



Hypsiglena. 



Salvadora. 



Rhinechis (also Holarctic of Eurasia). 



ChionacUs. 



Tr'nnorphodon. 



TantiUa (also in Brazilian Neotropical). 



Cinosternum (also in Brazilian NeotrojMcal). 

 The following genera of the Sonoran subregion enter the Texan dis- 

 trict of the Austroriparian subregion : 



Holbrookia. Hypsiglena. 



Grotaphytus. Rhinochilus. 



Phrynosoma. Cinosternum. 

 Oerrhonotus. 



Many species are peculiar to this subregion, as will be shown later on. 



The Western subregion is distinguished by the absence of most of the 

 types of fishes of the humid part of the continent, and the ])resence 

 of a few. Thus, the Ginglymodi. Ilalecomorphi, and Catostomidai are 

 absent, while Percomorphi are present. The Batrachian fauna lacks 

 the Proteida, Trachystomata, and Amphiumoidea, while Urodela are 

 abundant, excepting (h-yptobranchidiv. All the families of Salientia 

 characteristic of Medicolumbia are present except the EngystomidtE. 

 Xmong reptiles the genus Gharina is entirely characteristic, and Gerr- 

 honotus of the Toltecan and Sonoran fauna langes its entire length. 

 It is especially distinguished by the absence of the following genera: 

 First, all of the Iguanidai exclusively characteristic of the Sonoran 

 fauna, there remaining only Grotaphytus, Sceloporus, and Phrynosoma, 

 which also enter the Texan district of the Austroriparian ; by the absence 

 of Heloderma, Ophisaurus, and Liolepisma. Among snakes, by the 

 absence of true water snakes (genus Natrix), and the small burrowing 

 Natricinai of Opisthoglyph forms, and of poisonous snakes of the genera 

 Elaps and Sistrurus. No genus but Gharina can be cited as of universal 

 distribution, which is not at the same time found in some other subre- 



