XI. ON A NEW RACE OF CALLOSCIURUS 

 ATRODORSALIS vGRAY) FROM NORTH SIAM. 



By H. C. Robinson & R. C. Wroughton. 



CALLOSCIUKUS ATRODORSALIS ZIMMEENSIS, Sttbsp. 110V. 



Type: Adult female (skin and skull), British Museum No. 

 9, 10, ii, 20. Collected at Chiengmai, North Siam, on 12th 

 April 1908 by Mr. T. H. Lyle and presented to the National 

 Museum. Collector's Number 245. 



Diagnosis. A local form of C. atridorsalis, in which the 

 dorsal patch is almost obsolete and the rufous undersurface 

 broken by a patch, coloured like the back, on the throat, chest 

 and a narrowing area of the abdomen. 



Colour. General colour above the usual olivaceous grizzle, 

 the dorsal black patch almost obsolete; below the throat, chest 

 and a wedged shaped area, extending to at least half the length 

 of the abodomen coloured like the flanks, the remainder nearly 

 hazel. Face like back with no trace ol the bright colouring 

 so characteristic of tvpical C. a. atrodorsalis. Hands and feet 

 finely grizzled, at least as dark as the back. Tail rather as in 

 C. caniceps concolor than in C. atrodorsalis, i.e. the fulvous 

 shading of the hairs so common in the latter almost entirely 

 absent in this form. 



Dimensions. External dimensions of the type, taken in 

 the flesh; head and body, 217; tail, 205; hindfoot, 49; ear, 21mm. 



Skull: Greatest length, 55; basilar length, 42; zygo- 

 matic breadth, 32; nasals 17; diastema, 12; upper-molar series. 

 10. 6mm. 



Remarks. A fine series of 12 specimens, all with one 

 exception taken between 700 and 1,000 feet in altitude, is quite 

 constant in showing the obsolescence of the black dorsal patch 

 and equally so in the encroachment of the dorsal colouring on 

 the throat, chest and anterior abdomen. An individual taken 

 at Muang Pai on the Salwin watershed shows intergradation 

 with other forms from British Burma. 



