78 Mr. N. A. Severtzow on the 



mammals, only perhaps with a greater mixture of Tibetan 

 and Mongolian types, unobserved on tlie Tian-shan table- 

 lands, such as Syrrhaptes tibetanus, Charadrius mongolicus, 

 Larus hrunneicephalus . Two other species, viz. Otocorys 

 elwesi and Budytes calcarata, are very numerous in Western 

 Tibet, in the Pamir, and in the Alai, and are found also, 

 though not so common, in the Tian-shan tablelands. We 

 may also remark that the steppe-types of the ornithological 

 fauna of Bash-Alai and Pamir, viz. Otocorys elwesi, Saxicola 

 isabellina, S. deserti, Syrrhaptes tibetanus, Charadrius 

 mongolicus, and Tadorna casarca, are also found in Tibet. 

 But of these steppe-types only the two species of Saxicola and 

 Tadorna casarca are common to the Pamir and Aral-Caspian 

 steppe, the Saxicolee even ranging into the northern Sahara, 

 while the remaining species, though belonging to the most 

 characteristic genera of the desert avifauna, are peculiar to 

 the tablelands of high Asia, where they represent closely 

 allied species of the lower hot deserts. Thus, instead of Car- 

 podacus mongolicus, peculiar to the highlands of Asia, we 

 have the closely allied C. githagineus of Sahara, Syria, and 

 Persia, and instead of Otocorys elwesi, we have O. brandti in 

 the Aral-Caspian steppe and 0. bilopha in the Sahara. In 

 these genera the steppe-species, especially those of Otocorys, 

 are near relatives to those living in the* tablelands of the 

 Pamir and Tian-shan. Greater differences exist between 

 Syrrhaptes tibetanus and S. paradoxus of the steppe, and 

 between Charadrius mongolicus and C. caspius. 



We can see from the enumeration of the Pamir birds pecu- 

 liar to the steppes, that they only constitute a small part of 

 its avifauna, their number amounting to only one eighth of 

 all the species which breed there, or seven out of fifty-four 

 species. The greater part of the Pamir avifauna consists of 

 Central-Asiatic alpine species, mostly land-birds, and of 

 species which are widely spread over the whole Palsearctic 

 region. These last are mostly Waders and Palmipedes. 



The greater part of the northern birds belonging to the 

 polar tundras are only seen in the Pamir during the time of 

 migration, and are not common. 



