1896.] Distribution of Batrachia and Reptilia. 897 
than the cooler; and as we advance northward many species 
disappear, while a few othersare added. The natural division 
of the eastern part of the continent is then in a measure de- 
pendent on the isothermal lines which traverse it, which accord 
also quite closely with its geologic history. 
The Floridan subregion is distinguished by the presence of 
several peculiar genera of Batrachia and Reptilia, and by a 
number of peculiar species. A special feature is the almost 
total absence of Batrachia Urodela. The genera are: 
BATRACHIA: : Seminatrix, 
Lithodytes, . Liodytes. 
Pseudobranchus. 
ae SAURIA: 
SERPENTES: | Rhineiira, 
Stilosoma, Spherodactylus. 
Rhadinexa, 
Lithodytes and Spherodactylus are West Indian Neotropical 
genera, and Rhadinza, besides being Neotropical, extends into 
the eastern part of the Austroriparian subregion. Five genera 
are then peculiar. The peculiar species will be enumerated 
later. Several species of mammals are confined to this region. 
The genera of birds that do not range north of it are, accord- 
ing to Allen: 
Certhiola Aramus Wad 
enæda Audubonia BASE 
Oreopelia Pigeons. . 
P TPE tes Phænicopterus. 
- Rostrhamus Haliplana | 
Polyborus \ Raptores. Ras } Terns. 
The isolation of the Floridan subregion is due to the fact 
that the nucleus of the peninsula (which is of Eocene age) was 
separated from the continent during the greater part of neocene 
time. Ifat at any time connected with the Antilles, the period 
was of short duration. - 
- The Austroriparian region possesses many peculiar genera of 
reptiles not found elsewhere, while the region north of it pos- 
sesses none, its genera being distributed over some or all of the 
