The relationship between the palaearctic and nearctic faunas 



281 



FIG. 48. World distribution of the Salamander genus Hydromantes, in California 

 H. platycephaliis Camp., in Europe H. genei Schleg. {Spelerpes fiiscus Schreib.). 

 The figured specimen is of the Californian species (from Stebbins, 1951). 



occurrence on this far inland spot. Otherwise it is restricted to the steppe region 

 north of the Caspian Sea and of western Siberia. B. eschscholtzi is the most primi- 

 tive member of the genus Blethisa (Lindroth, 1945b, p. 13) and Semenov (1935, 

 p. 275) regarded it as a "relictum faunae tertiariae elementum". It is an old 

 species with disjunct relict area. 



Among Vertebrates, the affinities in the south between Europe and North 

 America are restricted to common genera, or higher taxonomic units. The most 

 conspicuous cases are the following: — 



Fam. Umbridae, fresh-water fishes, named Mud-minnows, with genus Umbra, 

 has two species in North America and one in Europe, U. krameri Wahlb. {lacustris 

 Gross), restricted to the basin of the Danube. 



Among Salamanders (Urodela) there are two links suggesting a connection. — 

 (i) The famous Olm, Proteus anguineus Laur., a true inhabitant of the karst-caves 

 of SE Central Europe, possesses its closest relatives in the Mud Puppies, genus 

 Necturus, with 7 free-living species in eastern North America.— (2) The Pletho- 

 dontidae, abundant in North America, but lacking in Asia, are represented in 

 Europe (SE France, N Italy, Sardinia) only by a species of Hydromantes, genei 

 Schleg. (Spelerpes fuscus Schreib.), with two subspecies (Mertens & Miiller, 1940, 



