Ill 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 Hijlodes and one Engystoma, besides about twenty 

 Hylidae, extend into North America proper, while possibly the 

 Eaninae have entered the Neotropical region from the north. 

 Biifo is too cosmopolitan to assist om- 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-w-estern Andesian 

 province ; (2) the rest of South America. 



AECTOGAEA.— NoKTH A¥okld. 



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 Palaearctic. — Prevalence of Salamandrinae 

 (Salamandra* Cliioglossa^ Salamandrina^ IViton) ; I'roteidae 

 {Proteus angidnus*) ; S2Jeleiycs fuscus* — Biscoglossus, Bom- 

 hinator, Algtes* Bufo, Hyla arhorea, Felohates* Felodytes* Eana. 



2. Eastern Palaearctic. — Amphiumidae {Cryidohranclius) ; 

 Amblystomatinae ; Salamandrinae {Triton, Pachytriton* Tyloto- 

 triton*); Amblystomatinae. — Bomhinator , Bufo, Hyla arhorea, 

 Rana, Bhacophori/s. 



3. Nearctic- — Amphiumidae {Cryptohranchus, Amjyhuima*); 

 Proteidae {TyjJhloinoIgr,* JV^ecturus*) ; Sirenidae* ; Amblystoma- 

 tinae ; most Plethodontinae ; Desmognathinae.* — Discoglossidae, 

 Pelobatidae {ScapJiiopus*) ; Bufo ; Hylidae {Hyla, Acris, Choro- 

 jdiilus) ; 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. 



