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Show 1903.] OF THE PERCY SLADEN EXPEDITION. 237 no two can be found that are exactly alike, the set ranging in colour from uniform red to nearly uniform black, and varying as much in details as in general tone. The skulls also vary very considerably both in size and in the development of their bullae, the extremes appearing at first sight to be quite different species, but being connected together by every gradation. 17. SCIURUS LANGSDORFFI Brandt. cS. 1088, 1154, 1177, 1182, 1195. $. 1081, 1124, 1155. A valuable series representing the true S. langsdorffi, which name has been applied by various authors to many different members of the group. 18. RHIPIDOMYS ROBERTI, sp. n. d. 1023, 1140. A Rhipidomys intermediate in size of skull between the large species of the R. macrttrus-latimanus group, and the small ones allied to R. phceotis ; most nearly related to the latter. Fur of medium length ; hairs of back about 7-8 m m . in length. General colour above dull fulvous or " clay-colour," finely lined with black. Sides clearer and more buffy, bordered below by a clear ochraceous-buff line edging the pure sharply-defined white of the belly. Face like back, rather less heavily lined. Cheeks buffy, like sides. Eyes without darker rings. Ears of medium length, brown, not strongly contrasting with the general colour. Outer side of arms and legs like flanks, inner pure white on the fore limb down to the wrists, but on the hind limb only halfway down to lower leg, the fulvous passing round the ankles; hands and feet dull whitish. Tail fairly long, rather less hairy than usual in this genus, its basal inch furry all round and coloured like the body ; the remainder uniformly brown. Skull shaped most like that of R. benevoleus, although much larger. Supraorbital ridges fairly well developed, evenly divergent backwards. Outer plate of anteorbital foramen scarcely developed anteriorly. Palatal foramina of medium length, narrow and pointed anteriorly, broadly open posteriorly; not reaching back to the level of m.1 Interpterygoid fossa of normal shape, with rounded anterior border. Dimensions of the type, measured in flesh :- Head and body 110 mm.; tail 145; hind foot (s. u.) 25, (c. u.) 26-7; ear 16. Skull-greatest length 32 m m . ; basilar length 24*5 ; greatest breadth 16 ; length of nasals 11 ; interorbital breadth 5-6 ; breadth of brain-case 14 ; length of palate 13-6 ; diastema 8 ; palatal foramina 5 X 3-l ; length of upper molar series 4*8. Type. Adult <$. B.M. No. 3.7.7.67. Original number 1023. Collected 6 July, 1902. Although Mr. Robert's trunk measurement of the type of this species is slightly less than that given by Mr. Simons for R. phceotis, |