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Show 1881.J INDIAN SPECIES O F M U S . 549 Measurements. Head and Tail Hind foot Forearm Ear-conch Muzzle to 1 nnd hand , length...' ear Types, Kohrud, Persial. a-cS. in. 3*6 4-0 (2) •95 •55 (c) -89 6.?. m. (c) 3*5 3*9 •82 •94 •53 Gilgit (Dr. Sci C.&. m. 3*55 4*05 •86 •98 •54 •90 &?. in. 3*40 3-95 •82 •95 •54 •90 dly). «.?. in. 3*67 41 •84 96 •54 •92 This species is so very closely allied to the c o m m o n Mus sylvaticus, 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, m u ch 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. sylvaticus :- Hind foot *90 *88 *90 -87 '85 Muzzle to ear .. *86 -81 -84 -84 '77 These dimensions show that, in English individuals at least, the comparative proportions of the hind foot are very different from those of M. 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. O n 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 occipital foramina. With regard to the other characters certain specimens approach M. arianus very closely, though none quite equal it. 1 The dimensions -dven by M r . 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. 2 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 unfortunately does not mention whether it is so or not. |