RESULTS FROM THE MAMMAL SURVEY. 235 



Tomeutes pygerythms janetta, Thos. 



Sixteen from Yin and two from Monywa, both on the east ]jank 

 of the Chindwin. 



Passing now to a very different group of Squirrels, we find some 

 interesting points in distribution, even where the species have 

 ah'eady been described. 



The present form, which was described from Mandalay, is found 

 on the east bank of the Chindwin up to Yin, not penetrating at 

 all to the west, nor further northwards than that place, no squirrel 

 of this type therefore occurring till north of the Uyu at Homalin 

 there is a slight eastern irruption of the next species, and again 

 much further on at Kauktaung and Hkamti ; where there is the 

 form of T. similis described below. Southwards T. p. janetta ranges 

 to Mt. Popa and Pyawbwe, and a certain distance up the 

 Irrawaddy above Mandalay. 



We thus find that while the north and south line of the Chindwin 

 and Lower Irrawaddy is an absolute barrier to the extension of this 

 Squirrel westwards, the Upper Irrawaddy, above the junction, is no 

 such barrier, the species occurring indiscriminately on both sides. 



The cause of this difference probably depends on the greater 

 frequency or accessibility of temporary islands, joined sometimes to 

 one side and sometimes to the other, in the Irrawaddy as compared 

 to the Chindwin, although Mr. Shortrldge states that such islands 

 occasionally occur also in the latter river. But the very marked 

 way in which throughout the fine series of Squirrels in the present 

 collection the species of the East and West banks of the Chindwin 

 are different from each other makes it difficult to believe that such 

 island pontoons can be readily utilized for crossing the river. 

 Mr. Shortridge himself believes that the more rapid current of the 

 Chindwin breaks up the islands more quickly than in the Irrawaddy. 

 All these specimens, like the original ones, have a whitish hip- 

 patch, while none is present in most of our skins of true pygerythrus, 

 from Lower Burma. But we have come to the conclusion that this 

 difference is wholly one of season, and that in all the present group 

 of squirrels no thigh-patch is present during the winter months — 

 say, from December to March — while July and August specimens, 

 always have them. This seasonal variation would explain the differ- 

 ences observed in several other cases, notablj^ in the complicated 

 problem presented by the Himalayan forms T. lokroides and similis. 



Tomeutes lohroides, Hodgs. 



Squirrels representing this long known Nepalese and Sikkini 

 species occur all down the west bank of the Chindwin, from 

 Hkamti to Kin, only just trespassing across the river in one place, 

 at Homalin. This place we may note is in the area where no 

 east-bank species of the group occurs, T. similis being some way 



