FAUNISTIC PROBLEMS 221 



of the genus Pelobates which inhabit Europe. Only a 

 single species (P. syriacus) has been discovered in Asia 

 Minor. The others extend from western Europe to the 

 Caspian. Another genus (Pelodytes) of the family Pelo- 

 batidae has one species in Portugal and a second in the 

 Caucasus. All the other genera of the family are found in 

 the East, and are more remotely akin to Scaphiopus than 

 Pelobates is. Hence we may conclude that the distribution 

 of these two genera is distinctly favourable to the suggested 

 trans -Atlantic land bridge. 



Another interesting amphibian that I have alluded' to 

 (p. 137) is the newt Spelerpes, which, with the exception of 

 a single European species, is peculiar to America (see Fig. 8). 

 The centre of dispersal certainly lies in Mexico, from which 

 country various sections have spread northward into the 

 States, southward as far as Peru, and eastward to the island of 

 Haiti. That this discontinuous distribution could not have 

 been brought about under existing geographical conditions is 

 evident, nevertheless, since no fossil Spelerpes are known, we 

 can only judge of the age of the genus from its distribution. 

 Dr. Gadow * suggests the Oligocene Period, and thinks that a 

 north -Atlantic land connection, such as the one I have de- 

 scribed in the first chapter of this work, from Labrador to 

 Scotland via Greenland, might have brought about the exist- 

 ing range of Spelerpes. Since the single European species 

 inhabits only Sardinia and the mountains bordering the Gulf 

 of Genoa, while most suitable ground for its existence is found 

 further north, I cannot admit that Spelerpes fuscus reached 

 Europe in that manner. The land bridge by which it crossed 

 the Atlantic must have lain much further south. 



I have already alluded to the fact (p. 173), that there 

 is apparently a south-western and a south-eastern form 

 of the American glass snake (Ophisaurus ventralis), and 

 that both of them extend northward for considerable dis- 

 tances. The only other members of the genus are the 

 European glass snake (Ophisaurus apus), which inhabits the 

 Mediterranean region and is very like the American, and the 

 Asiatic species, which is found from the eastern Himalayas 

 to Burma. 



* Gadow, H., " Mexican Amphibians and Eeptiles," p. 244. 



