364 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



the Nile valley region in the later Tertiary (fig. 237) after Mada- 

 gascar had separated from Africa. 



Our review of the data as to the Bufonidae and the genus Bufo 

 indicates, then, that the Bufonidae are an Equatorian family, dating 

 back to the Triassic period, and that Bufo arose during the Creta- 

 ceous either in northern South America or in Asia-Malaysia, its 

 origin being two geologic periods, or more, later than the origin of 

 the family. It is worthy of comment that this ancient family has 

 retained its vigor through all the geologic periods since the Triassic 

 and that its perhaps most recently evolved genus, Bufo, now dis- 

 putes with the genus Rana the position of dominance among the 

 Anura. 



The HYLmAE (fig. 227, p. 291). 



The map showing the present distribution of this family is decep- 

 tive, for the great area in Europe, Asia, and Africa, where they 

 occur, denotes the presence of but one species and three closely similar 

 forms, indicating apparently the migration of but one species from 

 North ^Vmerica and its subsequent divergence into four species, or 

 subspecies. 



It seems clear that the Hylidae were developed in the Western 

 Hemisphere. They are now found in tropical America north of the 

 region of the former sea which separated the central and the souther] i 

 portions of South America (fig. 236). They are not known from 

 southern South America and it does not seem probable that they 

 ever were in the Argentina-Patagonia-Chile area. But Hylids are 

 in Australia and Papua, though not in New Zealand. How are 

 these complicated relations to be explained? The moist forests 

 of tropical America (Brazil to Central America) are now the 

 home of the majority of the genera and species of Hylidae. They 

 are peculiarh'^ adapted to forest life. Doubtless they evolved in 

 this region. The grassy plains of Argentina-Patagonia are less 

 suitable for them. If the Hylidae had evolved in tropical South 

 America during the Jurassic, they should have passed to Euro-Asia 

 by the Ecuador-California-Alaska-Siberia ridge (fig. 233), but they 

 did not. Had they evolved in the Guianas during the early 

 Cretaceous (fig. 234) they should have passed eastward to Africa, 

 but they did not. If they evolved in Argentina-Patagonia, this 

 region must at one time have been heavily forested, a thing not 

 in agreement with paleontological evidence, and if they were there, 

 it is remarkable that they are now unrepresented in this area. They 

 are found in North America on the grassy prairies, so it hardly 

 seems likely that change from forest conditions to the pampas should 

 have exterminated them in southern South America. These con- 

 siderations indicate the region of the Brazilian Highlands as the 



