CROCODILIANS, LIZARDS, AND SNAKES. 1207 



ward on the east side of the Sierra Nevada as far as, including the arid 

 region of British Columbia. It occupies the valley of the Itio Grande, 

 aud extends into Texas as far as the Kio Pecos. It extends south- 

 ward in western Mexico as far as Mazatlan. The Western nuhregion 

 extends from the Pacific coast to the Sierra Nevada to an uncertain 

 distance on the Lower Californian peninsula. At the north it crosses 

 the Sierra Nevada, skips the narrow strip of the Sonoran in Washing- 

 ton, and extends to the Rocky Mountains, including northern Idaho 

 and western Montana. The Toltecan ftiibregion in(;ludes the States of 

 Guanajuato, Mexico, and the adjacent elevated regions of Michoacan, 

 Oaxaca, and Puebla, including the Alpine regions of the southern Sierra 

 Madre. It is probable that another subregion should be added, the 

 Taynanlipan of Townsend. This is a dry region extending frf)m near 

 the mouth of the Kio Grande to the Kio Soto la Marina, in the State of 

 Tamaulipas, More information regarding the fauna of this country is 

 desirable. 



The faunal peculiarities of these subregions are well marked. The 

 three subregions included in eastern North America differ from all the 

 others in the abundance of their turtles and the small number of their 

 lizards. Prolific of life, this area is not subdivided by any marked 

 mitural barriers. Hence, though its species present great varieties in 

 extent of range, it is not divided into districts which are very sharply 

 defined. The warmer regions are much richer in birds, reptiles, and 

 insects than the cooler; and as we advance northward many species 

 disappear, while a few others are added. The natural division of the 

 eastern part of the continent is then in a measure dependent on the 

 isothermal lines which traverse it, which accord also quite closely with 

 its geologic history. 



The FlorUJan subregion is distinguished by the presence of several 

 peculiar genera of Batrachia and Keptilia, and by a number of i)e<*uliar 

 species. A special feature is the almost total absence of Batrachia 

 Urodela. The genera aie: 



TIATRACHIA. 



Lithodytes. Pseudohranchus. 



SERPENTES. 



Stilosoma. Uhadincca. 



ISeminatrix. lAodytes. 



SAIIRIA. 

 Bliinenra. Sph cvrodactt/his. 



Lithodytes and S2)ha;rodactyIiis are West Indian Neotropical genera, 

 and Zv'/tar/inrm, besides being Neotropical, extends into the eastern i)art 

 of the Austroriparian subregion. Five genera are then peculiar. The 



