in GEOGRAPHICAL DISTRIBUTION 75 



genera and species ; the total number of the latter being, accord- 

 ing 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 

 Eaninae 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. 



AECTOGAEA. 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, 

 Eaninae. Few Hylinae occur. 



The whole region can be subdivided into three sub-regions. 



1. Western Pa la e arc tic. Prevalence of Salamandrinae 

 (Salamandra* Chioglossa* Salamandrina* Triton) ; Proteidae 

 (Proteus anguinus*} ; Spelerpes fuscus* Discoglossus, Bom- 

 binator, Alytes* Bufo, Hyla arborea, Pelo'bates* Pelodytes* Rana. 



2. Eastern Palaearctic. Amphiumidae (Cryptobranchus) ; 

 Amblystoinatinae ; Salamandrinae (Triton, Pachytriton* Tyloto- 

 triton*'); Amblystomatinae. Bombinator, Bufo, Hyla arborea, 

 Rana, Rhacophorus. 



3. Nearctic. Amphiumidae (Oryptobranchus, Amphiuma*}', 

 Proteidae (Typhlomolge* Necturus*} ; Sirenidae* ; Amblystoma- 

 tinae ; most Plethodontinae ; Desmognathinae.* Discoglossidae, 

 Pelobatidae (Scaphiopus*} ; Bufo ; Hylidae (Hyla, Acris, Choro- 

 pkihts) ; Rana. 



II. PALAEOTROPICAL REGION. Characterised by the presence 

 of Apoda and by the great prevalence of Firmisternal Anura, 

 which amount to nearly 90 per cent of the total population. 



* indicates Amphibia which are peculiar to the respective regions or sub-regions. 



