1 86 ANURA 



CHAP. 



Most, if uot all, Hylidae are climbers, and many lead an 

 arboreal life, but it does not follow that all the " Tree-frogs " are 

 green. 



Tlieir distribution is very remarkable. To say that this 

 family is cosmopolitan with the exception of the African region, 

 is literally true, but very misleading. There are in all aljout 

 150 species, and of these 100 are Notogaean ; one-half of the 

 whole number, or 75, being Neotropical; 23 are Central 

 American, 7 Antillean, and about 18 are found in North 

 America. One species, Hyla arhorea, extends over nearly the 

 whole Palaearctic sub-region, and two closely allied forms occur in 

 Northern India and Southern China. Consequently, with this 

 exception of three closely allied species, the Hylidae are either 

 American or Australian. We conclude that their original home 

 was Notogaea, and that they have spread northwards through 

 Central and into North America. The enormous moist and 

 steamy forests of South America naturally suggest themselves as 

 a paradise for tree-frogs, and it is in this country, especially in 

 the Andesian and the adjoining Central American sub-regions, 

 that the greatest diversity of generic and specific forms has been 

 produced. Tt is all the more remarkable that similar forest- 

 regions, like those of Borneo and other Malay islands, are 

 absolutely devoid of Hylidae (while there are about a dozen 

 species in Papuasia), whose place has however been taken for all 

 practical purposes by correspondingly modified Kanidae, notably 

 the genus Rhacophorus. Lastly, the fact that tropical evergreen 

 forests of Africa and Madagascar possess no Hylidae, but are 

 inhabited by several kinds of tree-climbing Bhacojjhorus, points 

 with certainty to the conclusion that the origin of this large and 

 flourishing family of Hylidae was not in Arctogaea. 



The versatility and the wide distribution of the Hylidae 

 has naturally produced cases of convergent analogy, iind the 

 various species of one " genus " may be in reality a heterogeneous 

 assembly. Such an instance is proljably the genus Hylella, of 

 which four species live in the Andesian and Central American 

 provinces, wliile the two others occur in New Guinea and 

 Australia. 



The two North American genera Choropliilus and Acris, and 

 the Brazilian Thoropa, connect the Hylidae with the Cysti- 

 gnathidae, in so far as their finger-discs are very small, or even 



