SCIUEUS. 231 



under surfaces of the bodies of the cervical yertebrae are marked by a feeble 

 median ridge, and external to it, on the hinder margin on each side, a small well- 

 defined nodule is present. The under surfaces of the lumbar vertebrae, with 

 the exception of the last, are strongly ridged, and the ridge is prolonged for- 

 wards more feebly along the dorsal vertebras and is almost lost on the second 

 dorsal. 



I have examined a very extensive series of squirrels belonging to the various 

 forms above described, viz., ^S'. pygerythrus, S. caniceps, S. phayrei, and S. blanfordii, 

 and of others, which appear to indicate at least, if not to prove, that all of them 

 are in some way related to each other. 



Out of a large series of specimens referable to S. caniceps, the males illus- 

 trate three phases of coloming associated with a difference in the character of the 

 fur. The first is a grey, the second a yellowish, and the tliird a phase in which the 

 back becomes brilKant yellowish-red. 



In the grey phase, — and the squirrels presenting it are all adults, — the fur of 

 the upper parts is so identical with that of S. hlanfordii that it is impossible to dis- 

 tinguish between the two forms, in a series of skins laid out belly downwards. 

 The fur is grey all over, very finely speckled with black and greyish ; and the 

 tails of the two forms also are identical, being annulated with greyish and black 

 in such a way that there is a tendency to a ringing of the tail with these colours, 

 the tip in both being black. The feet also are nearly white or pale yellowish, as in 

 S. hlanfordii. But on examining the under parts, it is found that in these phases of 

 ^. caniceps they are grey, whereas in S. hlanfordii they are a beautiful rich orange, 

 and the feet are yellow. I have never observed a specimen with the under parts 

 similarly coloured to those of >S'. hlanfordii, but there is one example from Moul- 

 mein, which has a blush of yellowish all over the under parts, but very pale and of 

 a different tint from that of S. hlanfordii. 



In the grey phase the f m' is rather short and not so soft and long as in the next 

 phase. A specimen illustrates the transition from the grey to the yellowish phase, 

 the f m^ becoming longer and the pale bands of the hairs changing to yellowish, 

 commencing from below upwards and showing itself through the fur, which, 

 when pulled aside, is seen to be yellowish underneath, although the sub-apical, 

 pale bands have not yet changed from grey to yellow. It would appear that 

 this change may either take place generally over the upper parts or commence 

 at first in a restricted area, from which it gradually spreads and at last involves 

 the whole of the upper parts; the change may progress more rapidly in some 

 localities than in others. This is shown in a specimen in which the underlying, 

 yellowish tinge is distinctly visible over the upper parts, but in the dorsal Kne 

 from the base of the tail to the middle of the back, the change has proceeded more 

 rapidly, and the fur is long, and distinctly annulated throughout, yellow and black. 

 Ultimately, the yellow and black annulation involves the whole of the fur, and in 

 this stage the under parts have changed from grey to dusky yellowish and the feet 

 are dusky grey. But in those instances in which the fur changes from a dorsal 



