CROCODILIANS, LIZARDS, AND SNAKES. 



1205 



Baird' divided this rejiiou into three districts, which he termed the 

 Eastern, Central, and Western. The Eastern occupied eastern Xorth 

 America to the central plains, where they exceed 800 feet above sea 

 level. The Western included the territory between the Cascade and 

 Sierra Nevada Mountains and tlie Pacific Ocean. In my paper of 1875- 1 

 adopted the Eastern, Central, and Western districts (calling- the last the 

 Pacific), and proposed two other districts, namely, the Austroriparian 

 for the Louisianian division of the eastern of Verrill, and the Sono- 

 ran for the southwestern and Mexican Plateau fauna'. Merriam, ■ in 

 1800, proposed a dift'erent arrangement. Using the name Sonoran for 

 the entire Medicolumbian Region, he divided it into — 



(1) an Afid or Sonoran snbregion proper, occupying the tablo-land of Mexico, 

 reaching nortli into western Texas, New Mexico, Arizona, and southern California; 



(2) a Californian snbregion, occupying the greater part of the State of that name; 



(3) a Lower Californian snbregion; (4) a (Ircat Basin snbregion, occupying the area 

 between the Rocky Mountains and the Sierra Nevada, extending as far north as the 

 plains of the Cohinibia; (5) a Great Plains sul)region, occupying the plains east of 

 the Rocky Mountains, and extending north to the plains of the Saskatchewan ; and 

 (6) a Louisianian or Anstroriparian snbregion, occupying tlie lowlands bordering the 

 Gulf of Mexico and the Mississippi, and extending eastward south of the Alleglianies 

 to the Atlantic seaboard where it reaches as far north as the mouth of Chesapeake 

 Hay. 



According to his arrangement the Eastern region of Uaird and myself 

 is not mentioned. 



This classification may be api>licable to birds and mamnuils; but it is 

 not applicable to the fishes, batrachia, and reptilia, wliicli are much 

 more exact indicators of the histories of fauna;, owing to their inferior 

 powers of migration. The eastern district or snbregion is more nearly 

 allied, from this i)oint of view, to the Austrorii)arian than the latter is 

 to the Sonoran proper, or arid region. This is due, as Baird previ- 



' American Journal of Science, XCI, 1866. p. 82. 

 ■'= Bulletin, U. S. National Miisenni, >,'o. 1, 1875, p. 55. 

 3 North American Fauna, 1890, ^o. 3, p. 24. 



