72 AMPHIBIA CHAP. 



separated countries, or on the strength of their distribution we 

 may conclude that the genera in question cannot be related to 

 each other, and do not belong to the same sub-family or family 

 as the case may be. Such groups are the Engystomatinae 

 and the genus Spelerpes ; amongst reptiles the Eublepharidae, 

 Helodermatidae, Anelytropidae, Ilysiidae, Amblycephalidae. 



It is customary to represent the various regions and sub- 

 regions as if they had boundaries as fixed as political frontiers. 

 Such limitations are quite arbitrary, and what is of more im- 

 portance, they differ in reality according to the class or order of 

 animals with which we happen to deal. Moreover, there has 

 been, and is probably still going on, an exchange or overlapping 

 of faunas. Such debatable grounds are Central America and 

 the highlands of North-western South America. The famous 

 Wallace's line, between Borneo and Celebes, Java and Lombok, 

 is absolutely inapplicable to the Anura. From their point of 

 view the Austro-Malayan countries, Papuasia and Polynesia do 

 not form a sub-region of the Australian, but rather of the Palaeo- 

 tropical region. Concerning the Urodela, the division into Palae- 

 and Ne-arctic sub-regions is unjustifiable since Eastern Asia has 

 emphatically American affinities (cf. also p. 96). The Sahara 

 and the rest of Northern Africa are intimately connected with 

 Arabia, Persia, Afghanistan, and Northern India, just as equatorial 

 Africa and Madagascar possess strong faunistic relationship with 

 Southern India and the Malay islands. 



Limiting factors of distribution. Common salt is poison to 

 the Amphibia ; even a solution of 1 per cent prevents the develop- 

 ment of their larvae. Consequently seas, salt lakes, and plains 

 encrusted with saline deposits act as most efficient boundaries to 

 normal " spreading." But undoubtedly many individuals have 

 made long and successful voyages across the seas on floating 

 trees. Solutions of lime are likewise detrimental to many 

 species, and it is a general fact that limestone-terrain is poor in 

 Amphibian life, unless, of course, sufficient accumulation of humus 

 counteracts or prevents the calcareous impregnation of the springs 

 and pools in meadows. Salamandra maculosa is, for instance, 

 absent in Central Germany on the Muschelkalk, but it occurs 

 in abundance in neighbouring districts of red sandstone or 

 granite ; nor can the larvae be reared successfully in very 

 " hard " water. On the other hand, Proteus lives in the sub- 



