II. Neotropical region.–Characterised by Apoda, Aglossa (Pipa), abundance of Cystignathidae (Hemiphractinae,* Cystignathinae, and Dendrophryniscinae*), Hylidae (Hylinae and Amphignathodontinae*), numerous Bufonidae and Engystomatinae; Dendrobatinae*; the Raninae are represented by a few peculiar genera, mostly restricted to the Andesian province; the genus Rana occurs there in a few species only.
Absence of Discoglossidae, Pelobatidae and Dyscophinae.
Several species of Urodela, of the genus Spelerpes, extend from Central America into the Andesian province, one occurs in Hayti, and Plethodon platense in Argentina.
This region is by far the richest in the number of families, genera and species; the total number of the latter being, according to Boulenger, about four-ninths of the known species. The region comprises South America, Central America, and the West Indian islands. Central America is naturally debatable ground; one species of Hylodes and one Engystoma, besides about twenty Hylidae, extend into North America proper, while possibly the Raninae have entered the Neotropical region from the north. Bufo is too cosmopolitan to assist our conclusions. The occurrence of four species of Hylella in South America, one in Australia, and one in New Guinea indicate that this is not a natural genus.
From the point of the Amphibia the whole region can be divided into two sub-regions only: (1) The West Indian islands with Central America and the north-western Andesian province; (2) the rest of South America.
ARCTOGAEA.–North World.
Characterised by the absence of Cystignathidae.
I. Periarctic Region.–Characterised by the Urodela, these being almost peculiar to the region (cf. p. [96]). Absence of Apoda. Presence of Discoglossidae, Pelobatidae, Bufonidae, Raninae. Few Hylinae occur.
The whole region can be subdivided into three sub-regions.
1. Western Palaearctic.–Prevalence of Salamandrinae (Salamandra,* Chioglossa,* Salamandrina,* Triton); Proteidae (Proteus anguinus*); Spelerpes fuscus.*–Discoglossus, Bombinator, Alytes,* Bufo, Hyla arborea, Pelobates,* Pelodytes,* Rana.