338 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



mate scarcely equalled elsewhere for intensity of cold out of the Arctic 

 Regions. This high barren tableland extends from Afghanistan to Yu- 

 nau 5 it comprises the drainage-areas of the Upper Indus and the Sanpu, 

 and is bounded on the north in its western portion by the Kuenluen 

 range, but it is less defined and its boundaries less accurately known to 

 the eastward, although much light has been thrown upon the subject 

 by Prejewalski's explorations".* In the " List of Mammalia known to 

 inhabit the Thibetan Plateau", given by Mr. Blaudford, the only distinct- 

 ively southern genus is Equus, The only peculiar genus is Poephagus, 

 but the list is evidently quite incomplete, tbe only Bat given being a 

 species of Plecotus, and the only Insectivore a species of "Crocidura". 

 Budorcasj usually attributed to Thibet, is excluded, and several other 

 genera, as Nectogale, Uropsilus, and JEluropus, currently given as pecu- 

 liar to the Thibet plateau, are not mentioned. While the Thibetan plains 

 belong certainly to the colder division, so many types mainly restricted 

 to this region occur that the question arises whether it may not be 

 proper to recognize the region as a Thibetian Province of the Temperate 

 Subregion. 



North American Region. The North American Region has been divided 

 by Professor Baird into three "provinces", termed respectively "East- 

 ern", "Middle", and "Western". Though not co-ordinate in point of 

 differentiation with the divisions of the Europa30- Asiatic Region above 

 recognized as provinces, they nevertheless possess distinctive features 

 and form natural regions. They are of course far smaller in area, and 

 possess a'much smaller number of genera, but have about the same pro- 

 portion of peculiar generic and subgenqric types. 



In the subjoined tables an attempt is made to give lists of the genera 

 of the two primary divisions of the North Temperate Realm, with 

 approximate indications of their distribution in the various subdivisions 

 of the two regions.! 



* Proc. Zool. Soc. Lond., 1876, pp. 632, 633. 



t In these lists, as elsewhere in the tabulated lists given in this paper, it is not 

 assumed that the groups adopted as "genera" are always of co-ordinate value. The 

 equation attempted is doubtless open in many cases to criticism. While the attempt 

 is made to assume an intermediate position between undue conservatism and excessive 

 multiplication in respect to groups assumed by different writers as " generic ", the lists 

 can of course be considered only as provisional. Again, it is occasionally difficult to 

 decide whether certain genera should be assigned, even in a general way, to one of the 

 faunal divisions rather than to another. However defective the result, the intent has 

 of course been to give a fair presentation of the facts of distribution. 



