1896.] Distribution of Batrachia and Reptilia. 899 
Plotus, Conurus, 
Tantalus, Chamepelia, 
Platalea, Campephilus, 
Elanus, Helinga. 
Ictinia, 
All these genera, excepting the last, range into South America 
or further. 
Among mammals, but few species and one genus (Sigmodon) 
are confined to it. Lepus aquaticus and L. palustris, the cotton 
rat, etc., and a few others, are restricted by it. The fish fauna 
is very similar to that of the Eastern region. 
The Eastern subregion differs from the Austroriparian almost 
entirely in what it lacks, and agrees with it in all those pecu- 
liarities by which it is so widely separated from the subregion. 
No genus of mammals is found in it which does not range into 
other regions, excepting Condylura (star-nosed mole); but nu- 
merous species are confined to it, not extending into the Aus- 
troriparian. These number from twenty to twenty-five. Among 
birds, the following genera are, according to J. A. Allen, shared 
with the more southern region only: Quiscalus, Siwrus, Helmi- 
therus, Protonotaria, Parula, Mniotilta. No genus of Reptiles, 
and but one of Batrachians (Gyrinophilus), is confined to this 
region; but it shares all it possesses with the Austroriparian. 
It has but four genera of lizards, viz.: Sceloporus, Cnemido- 
phorus Liolepisma and Eumeces. 
The Sonoran subregion is characterized in the lower vertebrate 
fauna, by great poverty in fishes, batrachians and tortoises, 
and abundance of lizards and snakes. Among fishes it lacks 
the orders Ginglymodi, Halecomorphi and Chondrostei, and 
possesses only one peculiar group, the Plagopterine, a division 
of the Cyprinide. Of usual Holarctic types it possesses only 
Isospondyli (Salmonide) and Plectospondyli; Percomorphi 
and Nematognathi being absent. The rivers that intersect its 
central district contain these types, but they must be reckoned 
as belonging with their bottom lands to the Eastern subregion ; 
the high plains only belonging to Sonoran. The true drainage 
area of the Sonoran subregion is that of the Colorado. 
