NO. 14 THE RACES OF PELLORNEUM RUFICEPS — ^DEIGNAN 1 5 



series, this is, despite the heavy streaking, a whiter bird beneath than 

 any one of the seven precedent forms. 



Range. — Hilly country of northern Siam (excepting Chiang Rai 

 Province), on the vi^est south to Ban Kaeng Soi (lat. I7°45' N., 

 long. 99° 1 5' E.) and probably farther, on the east south to Muang 

 Lorn Sak (lat. i6°45' N., long. ioi°io' E.). 



Specimens examined. — Siam: North: Ban Kaeng Soi (i female), 

 Doi Ang Ka (i unsexed), Doi Samoeng (2 males), Doi Suthep (2 

 females), Chiang Mai (4 males, 4 females), Ban Chiang Dao (i 

 female), Doi Chiang Dao (2 females). Ban Huai Chang Tai (i 

 male), Ban Tong Pa Sa (i unsexed), Doi Nang Kaeo (i male, 4 

 females), Doi Khun Tan (3 males, i female). Ban Mae Mo (i male, 

 I female), Ban Mae Phun (i male). Ban Phai Thon (i female), 

 Muang Ngop (i male). Ban Nam Khian (i female), Doi Ta Kong 

 (i male), Muang Lorn Sak (9 males, 2 females). 



Remarks. — Unlike many other northern Siamese species, Pellor- 

 neum ruficeps shows no important differentiation to east and west of 

 the Khun Tan Range. Since P. r. chthoniiim everywhere ascends the 

 hills to the lower limit of the evergreen forest, it is plain that several 

 of the passes through these mountains could serve as funnels for its 

 distribution across them. 



On Doi Suthep it ranges unchanged from the plains at its foot to 

 about 3,000 feet, where the mountain evergreen begins. An appar- 

 ently isolated colony exists in the open hill forest of oak and pine 

 from 4,500 to 5,000 feet ; unfortunately, no specimens of this popula- 

 tion have been available for comparison with the lowland birds. 



N.B. — An aggregation of 19 examples from the lower Pa Sak 

 River (Ban Thawai Phra, Ban Manao Wan, Ban Kaeng Khoi), the 

 hills dividing the Chao Phaya system from that of the Mekong (Ban 

 Pak Chong, Ban Lat Bua Khao), the western part of the plateau of 

 eastern Siam (Ban Bua Yai), and the country between this plateau 

 and "Southeastern Siam" (Kabin Buri, Ban Aranyaprathet) cannot 

 be placed to subspecies at the present time. While all the localities 

 named lie near each other on the map, a peripheral line connecting 

 them would include just the territory where two, if not three, races 

 might be expected to intergrade. It is possible that the birds of the 

 lower Pa Sak must be identified eventually as atypical chthonium, 

 those of Kabin Buri and Ban Aranyaprathet as atypical examples of 

 the form of "Southeastern Siam," those of Ban Pak Chong and Ban 

 Lat Bua Khao as intermediate between chthonium and a hypothetical 

 race of the eastern plateau (which would be exemplified by the single 



