60 MR. O. THOMAS ON THE MAMMALS OF [Jan. 19, 



I cannot agree with Dr. Anderson as to the identity of the 

 genera Pteromys and Sciuropterus, which he has united on the plea 

 that the dentition is much the same in hoth, and that the distichous 

 arrangement is not purely distinctive of the smaller species, but is found 

 partially in some of the larger, while, on the other hand, some of the 

 so-called Sciuropteri really have bushy tails. He goes on to say, 

 " The wing-parachute in all the members of the group is the same, 

 although some naturalists have described it iu sagitta as having an 

 expansion in front of the fore limb which does not exist in the other 

 species ; but this is unquestionably an error." 



In order to settle the question, I have examined specimens in spirit 

 both of Pteromys and Sciuropterus, and I find that not only do both 

 have an antebrachial membrane, arising from the back of the cheek 

 and inserted in the front of the carpus, but that there really are im- 

 portant differences in the development and insertion of the parachutes, 

 comparable in some respects to those observable in the wing- 

 membranes of the Chiroptera, differences which, as in the case of the 

 antebrachial membrane. Dr. Anderson must have overlooked through 

 examining dried skins only. 



In Pteromys there is a broad well-defined interfemoral membrane, 

 inserted externally at the point where the tendo achillis is attached 

 to the calcaneum, and internally to the tail from two to three inches 

 from its base, and there is in some of the larger species nearly three 

 inches depth of membrane clear of the hind limb. 



On the other hand, in Sciuropterus there is either no interfemoral 

 membrane at all, or what there is merely consists of a slight expan- 

 sion of skin behind the knee, attached externally to the tendo achillis, 

 about halfway down, and internally to the hinder side of the hips 

 and never involving any part of the tail. 



The lateral membrane also is distinctly narrower, especially below 

 the knee, in Sciuropterus than in Pteromys, although the longer 

 fringes of hair in the former hide this fact in dried specimens. 



Adding to these differences the well-known one in the arrange- 

 ment of the hairs of the tail, to which I am unable to see the 

 exceptions mentioned by Di-. Anderson, and also those in the den- 

 tition described by various authors, I think that it will be admitted 

 that two such natural groups as Pteromys and Sciuropterus should 

 be allowed to stand as distinct genera. 



8. Sciuropterus pearsoni. Gray. 

 a. Machi, 7/5/81. 



This rare species would be naturally expected to occur in Mani- 

 pur. It has previously been recorded from Sikkim, Assam, and 

 Yunnan. 



9. SciURus iNDicus, Erxl. 

 a. S . Gurung R. 8/2/81. 



The present is by far the most easterly locality as yet recorded 

 for this species, and extends its known range very considerably, the 

 Terai region of Nepal (Hodgson) and Cuttack (Anderson) having 



