14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



lat. I3°-I4° N. : Rat Buri (i male), Ban Pong (2 males); lat. 

 I4°-I5° N. : Kanchanaburi (3 males), Ban Si Sawat (2 males, I 

 female) ; lat. i5°-i6° N. : 28 mi. E. of Ban Um Phang (i female). 

 Remarks. — Beyond such a minor distinction, from one population 

 to another, as a slightly more or less rich huffy wash on the under 

 parts (and this appearing capriciously), it is not possible to find any 

 character by which the rich material before me can be subdivided. 

 That birds of this plastic species should be almost uniform across 

 more than 1 1 degrees of latitude may be easily explained by the Malay 

 Peninsula's lack of natural barriers to north-south expansion. 



17. PELLORNEUM RUFICEPS subsp. 



One specimen has been seen from Pulau Langkawi, the large island 

 at the northern mouth of the Strait of Malacca just off the Malay 

 State of Kedah. In the bold streaking beneath and the very light 

 wash of buff, it differs strikingly from any one of the long series 

 of P. r. acrum from the adjacent mainland, but can be separated from 

 the race of northwestern Siam only by the rather deeper coloration of 

 its upper parts. I believe that a distinct subspecies will be found to 

 inhabit Langkawi and the neighboring Pulau Terutau. 



18. PELLORNEUM RUFICEPS subsp. 



Two specimens from southeastern Burma, one from Thandaung, 

 the other from "Pegu Yomas," do not agree with any one of the 

 several Burmese races already described. They have the upper parts 

 as in the form of northwestern Siam and the under parts with equally 

 bold streaks but on a ground color much like that of P. r. minus. They 

 are perfectly distinct from this last and probably represent a sub- 

 species confined to the valley of the Sittang. 



19. PELLORNEUM RUFICEPS CHTHONIUM, new subspecies 



Type. — U.S.N.M. No. 336631, adult female, collected at elevation 

 2,900 feet on Doi Suthep (lat. i8°5o' N., long. 98°55' E.), Chiang 

 Mai Province, northwestern Siam, on November 21, 1936, by H. G. 

 Deignan (original number 1932). 



Diagnosis. — Upper parts much as in P. r. acrum, but the feathers 

 of the uppermost back frequently with vaguely nigrescent centers ; the 

 central streaks of the feathers of the breast and sides of the abdomen 

 almost always broader and more numerous ; the buffy wash of the 

 under parts usually almost restricted to the flanks and breast (where 

 it often forms a fairly distinct pectoral band), with the result that, in 



