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Show 234 MR. O. THOMAS ON THE [Apr. 16, head 18, breadth 18 ; heel to front of last foot-pad 23 ; length of last foot-pad 7*0. Skull: tip of nasals to centre of fronto-parietal suture (" bregma ") 36 millim.; nasals, length 21, greatest breadth 6*0; interorbital breadth 7'7 ; outer wall of infraorbital foramen, length 4*7 ; palate, length 26*5 ; length of palatal foramen 7*9 ; diastema 13*6 ; length of upper molar series 9*4. Dimensions of a fine female in spirit, preserved in the Museo Civico, Genoa:-Head and body 230 ; tail 393 ; hind foot 49 ; ear 20 ; heel to front of last foot-pad 25 ; length of last foot-pad 8*8. This spirit-specimen was obtained by Signor Beccari at Sungei Bulu, W . Sumatra, thus affording another instance of the relationship between the mountain-faunas of Sumatra and Borneo. Its examination, which I owe to the kindness of m y friend the Marquis of Doria, has enabled m e to add certain particulars, only observable in spirit-specimens, to the original description of this species. Mus sabanus belongs to a well-marked group of Rats which contains Mus jerdoni, Biv., M. niveiventer, Hodgs., M. coxingi, Swinh., M. edwardsi, Thos., M. hellwaldi, Jent., M. alticola, Thos., and others. These species are, however, all very much smaller than it is, with one exception, M. edwardsi, which is as much larger, and not one of them has a tail of anything like the extraordinary length of that of Mus sabanus. One species, indeed, also a native of Borneo, has a certain superficial resemblance to the present one, although belonging to quite a different group of Rats. This is M. muelleri, Jent., of about the same size, and with a nearly equally long tail ; but it may be readily distinguished by its coarse Mus decumanus-\ike fur, yellowish instead of rufous coloration, the less sharply defined white underside, and by the quite uniformly brown-haired feet and tail. 16. Mus LEPTURUS, Jent. a. Ad. b. Imm. 3000 feet. 24/3/88. Described by Dr. Jentink from Javan examples now in the Leyden Museum. 17. Mus ALTICOLA, Thos. Ann. Mag. N. II. (6) ii. p. 408 (1888). «, 6. eS 2- 8600 feet. 24/2/88. 2 • Type. Fur mixed with flexible spines both above and below. General colour above a peculiar bluish grey, not speckled or grizzled, darker along the median line. Dorsal hairs and spines creamy white basally, gradually darkening to grey terminally. Underside pale yellowish white, the hairs and spines uniformly of this colour to their bases ;. the line of demarcation on the sides not very sharply defined. Hands and feet white, the hairs short and fine, fifth hind toe (without claw) reaching nearly to the end of the first phalanx of the fourth. Tail finely ringed, the rings averaging about 10 or |