| OCR Text |
Show 1891.] MAMMALS F R O M E A S T E R N AFRICA. 185 Colour a coarsely grizzled brownish yellow mixed with black, the grizzling appearing all the coarser from the great length of the fur. Longer hairs on centre of back black-tipped, those on sides yellow-tipped. Bases of hairs all over, above and below, pale slaty grey for seven-eighths of their length; tips of belly-hairs dirty yellow. Ears, as usual, large and rounded. Tail short, bicolor, black along the top, shining greyish white along the sides and under surface. Skull very m u c h as in O. irroratus, but the bones rather lighter and more delicate. Teeth. Upper incisors narrower and flatter in front than in 0. irroratus; their anterior faces each with one deep groove in the position of that of O. irroratus, a faint internal one also as in that species, and between the two a third very faint and indistinct one, just flattening the part of the tooth that is most convex in the allied species. Lower incisors each with two deep and distinct grooves, the outer one clearly corresponding to the single groove in O. irroratus, the inner one running along the part that is so prominently convex in that species. Lamina formula of molars '^j^ as in all the present set of 0. irroratus. Dimensions :-Head and body approximately 120 millim. ; tail (of b, that of a being broken) 47 ; hind foot 25*5. Skull. Basal length 31'4, greatest breadth 18'1; nasals, length 16, breadth 6*2; interorbital breadth 4 ; interparietal, length 4*9, breadth 9"5; anterior palatine foramen 6*5; diastema 7'7 ; length of upper molar series (crowns only) 7*8 ; combined breadth of upper incisors 3'6 ; lower jaw, condyle to incisor tip 23'8. As already shown, the more numerously grooved incisors separate this new species at once from O. irroratus, while O. brantsii, Smith, and 0. unisulcatus, F. Cuv., the only other species recognized, have incisors even less grooved than in the form to which I have compared it. It represents therefore a most interesting step towards Oreomys typus, Heugl.1, a native of the high mountains of Abyssinia, which has no less than three deep grooves on each of its incisors and a lamina formula of ^^-; in fact its discovery may necessitate the union of" Oreomys" with Otomys, the number of incisor grooves being in this group evidently not a generic, but only a specific character. Without having examined a specimen of Heuglin's animal, however, and only from his description, I do not care for the present definitely to abolish the genus. This striking new species is one of the many important zoological discoveries made by Mr. Jackson during his ascent of Mount Elgon iu January 1890, and it is with much pleasure that I connect with it the name of so distinguished an explorer and naturalist as he has proved himself to be. 1 Eeise N.O.-Afr. ii. p. 76 (1877). 2 Heuglin, in his description, stated that there were 4 upper molars present in Oreomys, with a lamina formula of 3-2-3-5; but he had evidently mistaken the long posterior tooth for two, and I have therefore corrected his formula into that above given. |
