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Show 1900.] MUS SYLVATICUS AND ITS ALLIES. 421 ligne mediane des flancs et des cotes du cou, d'un brun-roussatre dore ; la tete est d'une teinte brune et les longues moustaches sont d'un brun cendre. La couleur blanche de toutes les parties inferieurs s'etend jusqu'a la ligne mediane des flancs et des cotes du cou ; les quatres extre'mites sont aussi d'un blanc pur." The skull is about equal in size to that of M. sglvaticus and with an identical tooth-pattern; the total length of skull of no. 88.9.25.6 (damaged) is slightly over 24 m m. Distribution. Known only from Japan. General Remarks. The only specimens of this Mouse at my disposal are nos. 88.9.25.6 and 88.9.25.7, collected by Mr. H. Pryer, and which bear on the labels the simple locality " Japan." The latter is a female with the mammas arranged as in 31. sglvaticus, and, since the general pattern of coloration and teeth, and skull, where not damaged, also agree with that species, I can have no hesitation in regarding this Mouse as very closely allied to M. sylvaticus. The dimensions of the dried skins, however, seem to show that the animals are considerably smaller than average M. sglvaticus. Although Temminck gives no particulars as to tbe skull of his M. argenteus, and although his figure of that species is a miserable caricature of a dark brown M. musculus-like Mouse, with dark feet, long tail, and light underside, his description, which, it will be noted, contradicts his figure in several important respects, fits this Mouse so closely that I feel bound to identify it as Mus argenteus. I can have little doubt that this Mouse is a local development from a sylvaticus-like stock, in which the skull has not altered from that of the type, but its peculiar red colour, its size and proportions mark it, as might perhaps have been expected, as the most distinct ally of 3Ius sylvaticus which I have seen. M0S ORTHODON. Mus orthodon,^. Hensel, Zeitschr. deuts. geol. Gesellsch. 1856, p. 279, pi. xiii. figs. 6-10 (aff. Muri sylvatico, fide C. I. Forsyth Major, P.-verb. Soc. Tosc. 1888, p. 129). Type (skull) from the Ossiferous Breccia of Mt. San Giovanni, Sardinia. In dealing with Mus sylvaticus, I must allude also to Mus orthodon, which is believed to be very closely allied to it, and the skulls and teeth of which in the British Museum Collection I have examined. The teeth of this species are far more hypsodont in character, and in immaturity show very deep lateral grooving of the crowns, so that they are also more Vole-like than those of modern 31uridce. The first upper molars of the youngest specimen show three internal and three less distinctly marked external convexities. The tubercles have been a good deal worn away, so that their exact disposition can only be guessed ; but the teeth certainly give the impression of having had all the nine tubercles of Hensel's diagrams present and regularly arranged when quite PROC. ZOOL. Soc-1900, No. XXVIII. 28 |
