I88l0 



INDIAN SPECIES OF MUS. 



Measurements. 



549 



This species is so very closely allied to the common Mus sylva- 

 ticus, L., that I think it is extremely doubtful whether it is more 

 than a variety of that species. The external characters (size, colour, 

 and proportions), with one exception, are identical with those of 

 English specimens of M. sylvaticus ; the one exception is the length 

 of the hind foot, which in M. sylvaticus is remarkably long, much 

 more so than is usual among the species of restricted Mus, while in 

 M. arianus this part is only of normal length. Thus, the hind 

 foot of true M. sylvaticus is distinctly longer than the distance 

 between the muzzle and ear, while, as shown by the measurements 

 given above, that of M. arianus is always shorter. The following 

 are these two measurements in five English specimens of M. sylva- 

 ticus : — 



Hind foot 



Muzzle to ear . . 



These dimensions show that, in English individuals at least, the 

 comparative proportions of the hind foot are very different from 

 those of J/, arianus ; but I have not been able to examine any 

 properly-preserved specimens from intermediate localities, so that I 

 cannot give a definite opinion as to the constancy of this character. 



With regard to the skull, Mr. Blanford, in his Zoology of the 

 Yarkand Mission, has discussed the question of the relationships of 

 these two forms. He there states that in M. arianus the occipital 

 portion of the skull is lower, as also is the foramen magnum, the 

 opening of the posterior nares is broader, and the last upper molar 

 is larger than in M. sylvaticus. On comparing the typical skull of 

 M. arianus with a series of skulls of M. sylvaticus, I find that a 

 Lanarkshire specimen has a lower occipital region, and that of 

 several British specimens some have higher and some lower occi- 

 pital foramina. With regard to the other characters certain speci- 

 mens approach J/, arianus very closely, though none quite equal it. 



1 The dimensions given by Mr. Blanford, being those of the specimens when 

 fresh, are not suitable for comparison with those of specimens preserved in 

 spirit. I have therefore re-measured the types in the British Museum. 



- The hind feet of this specimen have been broken. Mr. Blanford gives 

 their length as -9 ; but this, I believe, includes the claws, though he unfortu- 

 nately does not mention whether it is so or not. 



