REPTILES. 235 



Of the division of the frogs some species are found in every 

 region of the world. The genus of the tree-frogs is peculiar to 

 temperate and warm countries, and the species belonging to it are 

 especially numerous in America. The genus Pipa belongs exclu- 

 sively to South America. In Africa only few species of toads and 

 frogs are met with. Most of the genera of serpents, particularly 

 those of poisonous serpents, belong to warm regions ; the rattle- 

 snakes (Crotali) are found in America alone, the spectacle-serpents 

 (S'ajce) only in the old world. Amongst the serpents that are not 

 poisonous the Pythons belong to the eastern hemisphere, the Boas, 

 some smaller species excepted, to America. Africa has only few 

 species of serpents ; in most of the islands of the southern Pacific 

 they are absent entirely. Amongst the lacertine animals most of 

 the forms are restricted to warm countries, especially the family of 

 the Iguanoi'ds so rich in species. The genera Chamceleon, Varanus 

 and Agama ( Trapelus) , are proper to the eastern hemisphere, the last 

 almost exclusively to Africa ; to Asia in particular that of the flying 

 lizards (Draco) is limited, and the sub-genus of the Gavials; to 

 America, on the other hand, the sub-genus of the Caimans or A lli- 

 gators, amongst the crocodiles, belongs; in America exclusively 

 are species of the genera Anolis, Polychrus, and some others of 

 the Iguano'ids found, whilst still other genera are common to both 

 hemispheres. Amongst the tortoises, the genus Chelys or Matamata 

 is peculiar to South America alone ; the land-tortoises ( Testudines) 

 are found in the warm regions of the old and new world, especially 

 in Africa ; the turtles also are most numerous in the seas of warm 

 regions. Of the fresh-water tortoises different species are found 

 indeed in temperate regions, principally of North America, yet still 

 the greatest number belong to tropical lands. Since then some 

 species of lizards, serpents and frogs are found in cold regions 1 , 

 of which the frogs are the most numerous in species and especi- 

 ally in individuals, whilst, on the contrary, no tortoises live in these 

 regions, being limited to warm countries, the frogs and tortoises 

 thus form the two extremes in the geographic distribution of the 

 reptiles : of which the first-named have the widest dispersion in 



1 In Sweden, for instance, Coluber natrix, Vipera berus, Lacerta agilis are 

 found. 



