22 BULLETIN 186, UNITED STATES NATIONAL MUSEUM 



Chiang Rai also possesses a small number of forms that have pre- 

 sumably evolved in this part of the Indo-Chinese * peninsula and find 

 within that province their entire Thai range ; some of them are Aegi- 

 thhia t. sty aid and Gamrulax m. schauenseei. 



WEST 



The two provinces that together form the western division of our 

 area are almost entirely mountainous, but along the rivers are em- 

 bouchures of greater or lesser width upon which lowland birds find a 

 congenial home. The mountains, with bases at 1,000 feet, reach at 

 some points to more than 8,000 feet; it is then not surprising that the 

 division possesses an avifauna of remarkable richness. 



The majority of lowland birds are not racially separable from those 

 of Pegu. The montane fauna is almost identical with that first made 

 known by Davison and Hume from Mount Muleyit; indeed, Muleyit 

 is but the southernmost peak of the range, which is called by the Thai 

 the Thanon Thong Chai and which, except for Muleyit itself, runs 

 wholly through Thai territory. 



It is my opinion that Kloss should have continued his line between 

 "Western Siam" and "Central Siam" north along the line of the Khun 

 Tan range, calling the whole narrow strip along the Burmo-Thai 

 frontier "Western Siam." (Map 4.) Western Thailand itself would 

 then require a further division into northern and southern portions 

 with the line of separation running between the southernmost peak of 

 the Thanon Thong Chai and the northernmost of the Tanao Si range 

 (just southeast of Muleyit). The fauna of these hilly districts from 

 Muleyit north as far as Doi Chiang Dao is quite uniform ; on Doi Pha 

 Horn Pok (and probably other peaks of the Daen Lao) we find a new 

 fauna belonging rather to the Shan States and Yunnan, but since these 

 mountains are on the frontier and are little known I am not yet willing 

 to treat them separately from my western division. 



EAST 



The three provinces that I combine into an eastern division are for 

 the most part hilly but without peaks of sufficient elevation to support 

 a montane fauna except in the northeastern corner of Nan; the avi- 

 fauna is therefore necessarily less rich than the one just discussed. 

 Within its limitations, however, it differs strikingly from that of the 

 western division by completely lacking many characteristic Inclo- 

 Burmese species, by the possession of many characteristic Indo- 

 Chinese species, and by the fact that, in such species as range con- 

 tinuously from eastern Burma to Laos and are represented in the two 



1 1 have consistently used the name Indo-China for the entire peninsula, the name In- 

 dochine for those territories governed by the French. 



