CLASSIFICATION OF THE SCIURIDiE. 225 



a'. Lower edge of shaft tolerably evenly convex tlirongliout or convex 

 beneath lower end of long hinge, distal end not expanded, without 

 strong]}- convex edge. 

 6. Apex of blade some distance from proximal end of shaft, lower 



edge of blade with sigmoid curvature daivsoni. 



h\ Apex of blade a little behind proximal end of shaft, lower edge of 

 blade without sigmoid curvature. 

 c. Lower edge of blade evenly emarginate, distal end of shaft not 



thickened .' rtifigenisfiiscus. 



c'. Lower edge of blade straight up to angular notch by hinge ; 

 distal eml of shaft to which blade is hinged somewhat ex- 

 panded loJcriah. 



In three species of A^annoscmrus — A\ tohiteheadi from Kina 

 Balu, iV. exilis from Borneo, and iY. microtis from iSarawak — the 

 proximal end of the shaft of the baculum is not thickened and 

 elevated, and its upper edge, as far as the hinge of the blade, is 

 almost straight, and is parallel in a general way to the lower edge 

 of the blade ; the tip of the blade just reaches the base of the 

 shaft. In jy. whiteheadi and JSF. exilis the lower side of the shaft 

 has a rounded swelling near the middle, and the distal end is only 

 a little raised ; the blade is arcuate with serrated upper edge and 

 a narrowed point. In iV. lohiteheadi the apex of the shaft, to 

 which the blade is hinged, is thicker, and the blade itself is more 

 arcuate and more strongly serrated than in N. exilis. In 

 iV. microtis the shaft has no definite inferior thickening, its 

 distal half is bent up at an obtuse angle, the blade is not arcuate 

 nor serrate, and the tip is bluntly rounded and scarcely nari^owed 

 in profile view. (Text-fig. 22, H-K.) 



The measurements of these bacula are as follows : — N. tohife- 

 headi 5 mm., N. exilis 4 mm., iV. microtis 3 mm. 



In the following table the characters of the bacula of the three 

 species of Nannosciurus, here described, are briefly summarised : — 



a. Shaft with its distal half bent up at an obtuse angle without a 

 rounded thickening near the middle of its lower surface ; blade 

 with tolerably straight, smooth upper edge and widely rounded 



tip microtis. 



a'. Shaft tolerably straight axially from end to end, the extreme apex 



a little elevated, a conspicuous thickening near the middle of the 



lower surface ; the blade long, apically attenuated , with upper edge 



convex and serrulate. 



h. Blade high and arched, with wide space between its lower edge 



and the shaft wliiteJieadi . 



h'. Blade lower, less arched, a much narrower space between its 



edge and the shaft exilis. 



The Oi-iental Squirrels thus fall into three main groups, judged 

 by their bacula : — 



1. Rheithrosciurus, belonging to the same group as Sciurus of 



the preceding section. 



2. Ratufa, Funamhulus, and Tamiodes, with simple bacula. 



3. Gcdlosciurus, Tomeutes, Tamiops, Lariscus, Nannosciurus^ 



etc., which have compound bacula provided with a blade. 



