66 Zoological Society : — 



streak, which is darker on the back, black on the crown, and indi- 

 stinct on the nape ; beneath rather paler, with a broad white lon- 

 gitudinal streak near the middle of the chest and front of the abdo- 

 men ; ears produced beyond the fur, naked internally ; the skull 

 with a very deep concavity between the orbits. 

 . Hab. Batchian. 



This species is most like Cuscus orientalis ; but in that animal the 

 male is pure white. It differs entirely from G. celebensis (from 

 Celebes) in the general colour of the fur, and in having a distinct 

 streak on the head and back, somewhat like the streak on the back 

 of the female G. orientalis, but narrower and darker. 



It differs from all the other species in the nakedness of the inner 

 surface of the ears. 



The white streak on the chest and belly is not exactly in the 

 middle of those parts ; and there is a square white spot on the upper 

 part of the right fore leg, not found on the other legs. 



This animal may possibly be the coloured male of C. orientalis ; 

 but all the known males of that species are pure white. Can albi- 

 nism be the usual, and this coloured male the unusual, characteristic 

 of that species ? 



The skull of Mr. Wallace's animal from Batchian agrees in general 

 character with the skull of G. orientalis (sent to the Museum as 

 Guscus Quoyii from the Moluccas), but is yet sufficiently unlike to 

 render it very doubtful if it be not a distinct species. It is smaller ; 

 the impression on the crown is deeper and furnished with a much 

 more decidedly raised edge, which is extended behind on the central 

 line to the occiput ; and there is a notch or ridge at the upper front 

 angle of the orbit, not to be found on the skull of C. orientalis. 



Some of the converts to the theory of the mutation of species 

 may think that this animal is an instance in point ; but such a hy- 

 pothesis derives no support from the observations I have made. 



All the difficulties here started arise from the imperfect material 

 which the specimen affords for arriving at any definite opinion on the 

 subject ; and I believe that this is the explanation of nine-tenths, or 

 I may say ninety-nine in a hundred, of the cases on which the theory 

 is attempted to be established. This is not to be wondered at when 

 we consider how very few are the animals, even of our own coun- 

 try, and more especially of exotic species and genera, whose history 

 and anatomy have been properly studied. Most naturalists are of 

 necessity in the habit of describing species from the few specimens 

 which are brought from abroad in a more or less perfect state, with- 

 out being acquainted with the changes which the animal undergoes 

 in growing from its birth to maturity, and without the slightest in- 

 dication of its habits and manners. Now, we know from experience 

 amongst the British birds (such for example as the Rook and the 

 Crow, and the species of the Willow Wrens) , that if we were called 

 on to describe them from such materials we might make great mis- 

 takes. A mere examination of stuffed specimens might well lead 

 to doubts as to their distinctness as species, but this could never 

 be the case if we had seen them alive in their native haunts, and 



