MUS. 311 



tooth, with a not very well-marked groove on either side of it, close to the sharp 

 line defining the lateral margins. Dr. Gray, however, describes these teeth in 

 Vandeleuria as having a deep groove near the middle on the oblique front edge. 

 Such another discrepancy as this between the teeth of these mice I am dealing 

 with and Dr. Gray's Vandeleuria make me hesitate to pronounce them the same. I 

 have before me mice agreeing with Elliot's specimens from the valley of the Upper 

 Godavery, from Berar, Allahabad, Katmandu, Nepal, Assam, Burma, and the 

 Kakhyen hills, and all of which have their upper incisors grooved as I have just 

 described them. If the molar dentition is compared with that of M. Jiomurus, 

 a mouse about the same size, the characters wherein it differs from that of ordinary 

 mice will be broiight out. In M. homurus there are transversely three cusps to 

 the first and second folds, wliile there are only two cusps to the third fold, the 

 inner cusp not being developed. In this long-tailed arboreal mouse the same 

 number of cusps exist, but the outer cusp of the third fold is not developed, or 

 only very feebly so. The folds are much more bent on themselves at their middle 

 through the mesial cusp than in M. homurus and M. urbanus. In the former 

 there are two folds to the second molar and three cusps to each fold, the poste- 

 rior external cusp being the least developed. In this mouse the second tooth has 

 two mesial cusps, one behind the other, the posterior being somewhat backwardly 

 elongated. External to the anterior of these cusps there are two small cusps, 

 and internally one large cusp tending to divide in two. External to the posterior 

 central cusp there is one small cusp, and at its internal border only a ledge of the 

 cingulum. In the last molar of M. homurus there is one small central fold, the 

 inner end of which tends to form a cusp, with another anterior to the latter 

 internally and one behind it. In these supposed examples of Vandeleuria there is 

 one fold so bent on itself that it encloses an islet in its centre, and externally 

 it gives off a small cusp, a part of the fold nearly constricted off, and anterioi' 

 to the hinder end of the external extremity of the fold. Behind the point where 

 the two ends of the fold come in contact posteriorly, there is a well developed 

 cusp (unicuspulate fold). 



The first fold of the first lower molar of M, homurus is divided into two cusps, 

 which is also the case more or less with these supposed examples of Vandeleuria, and 

 the external cusp of the tliird fold of Vandeleuria is much less developed than in 

 31. homurus. The other teeth differ but httle. Erom this description it is evident 

 that the dental characters by which these forms differ from ordinary mice are not 

 at all well defined. 



The form of the skuU is much the same as in Mus, but the skull presents a 

 structural difference at its base, which, taken in conjunction with the grooving of 

 the incisors and the absence of a true claw on the 1st and 5th digits of both feet, 

 would seem to entitle this form to sub- generic rank, but not to more. 



The features to which I allude are the structure of the posterior nares, 

 pterygoid fossa, and infraorbital foramen. The former, instead of being narrow 

 and short, as in mice generally, are wide and long, and on looking into them from 



