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Show 1900.] MUS SYLVATICUS AND ITS ALLIES. 419 The skull is narrower and slightly smaller than that of adult of the subspecies intermedins, reaching a length of only about 25 mm., and having the anterior portions of the frontals more attenuated, and the nasal region proportionately more slender than in the latter subspecies. Distribution. At present known only from the typical series. General Remarks. The Mice identified by Mr. Oldfield Thomas as 31. chevrieri form quite a nice series of eleven specimens, with which may be considered eight specimens collected by Mr. C. B. Bickett in the same locality. Although obviously representing a subspecies of 31. sylvaticus, I am unable to identify them with any known phase of that species. They cannot be 31. chevrieri, for they are not larger, but rather smaller than the average ; and the colour of the upperside, although brighter than that of M. sylvaticus from Western Europe, is not like that of 31. confu-cianus. They cannot well be 31. s. arianus, Blanford, the description of which certainly does not apply to them, while they differ in more than one obvious respect from 31. s. intermedins. The series represents individuals of very varied age, from quite young specimens to adults. The young seem to undergo very different changes of colour in their progress to maturity from those undergone by 31. s. intermedins. W h e n very young, they are of a darker slate-colour; and they appear to retain the dull slaty hues of immaturity until they reach a considerable, perhaps their full, size. Thus no. 97.6.6.11, a nursing female, with mamma? 4 4-4, is in colour of the upperside very like an ordinary 31. musculus, but, unlike this species, has a sharply defined white belly. Another nursing female, no. 98.11.1.22, is in process of losing her immature coat, and presents a three-coloured appearance, having the belly white, the central dorsal region clothed in the dusky immature tints, while the flanks show the red colours of an adult. Another specimen has progressed farther, and shows traces of the dark colour only ou the rump. This patchy method of assumption of the adult coat seems to be quite unknown in M. s. intermedins, in which the process seems to be much more gradual; it would appear to be highly characteristic of this new subspecies. The wrhite belly is present in specimens of all ages, and two or three show a breast-spot or band of more or less complete development. The skulls of this subspecies are interesting, and are remarkable as compared with skulls of M. s. intermedins and even with the skull of the South Shensi specimen, as being very much narrower and more attenuated in the anterior frontal and nasal region. They are far less massive than in examples from Boumania, but almost equal in size those of medium-sized individuals from Western Europe. None of those which I have at my disposal are quite perfect, but the respective dimensions of total length and breadth would appear to be about 25 and 11 m m . The tubercles of the molar 1 are rather regularly arranged, and I think that the central tubercle of the last row (C" of Hensel) is more prominent than in M. s. intermedins. |
