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Show 1900.] MAMMALS EROM SOUTHERN ABYSSINIA. 81 8. ARVICANTIUS DEMBEENSIS. $ . Kombolsha, 16th February, 1899. " Shot close to water-side among reeds. Small colony ; native name ' Ait'." Measurements taken in the flesh-head and body 113 millim., tail 105, hind foot 26, ear 17. This species, described by Biippell in 1842, is represented in the British Museum by only a single specimen obtained by Dr. W . T. Blanford while accompanying Lord Napier's expedition to Magdala. The fur of this species is much softer and the annu-lations finer that in A. abyssinicus, and the belly is almost entirely white. The skull is rather less angular, and the palatal foramina are shorter, not reaching so far back as the first molar. The molars of the two species (see figs. A & B ) are strikingly different; the first upper molar of A. dembeensis is oval in shape, having only 7 cusps (the 8th being vestigial), three in the middle line with two inner and two outer of almost equal size placed in the intermediate spaces, so that the tooth is almost rose-shaped, six of the cusps surrounding the central one. It will be seen that the usual third outer cusp is almost entirely wanting. A B A. Eight upper molar series of Arvicanthis abyssinicus. B. Eight upper molar series of A. dembeensis. The second upper molar is formed of six cusps, two larger in the middle line and four smaller-two outer and two inner-set in advance of the larger pair, so that the front of the tooth is concave, and the hind part convex, being formed of the middle cusp only. The pattern formed by the cusps of these two molars is very symmetrical, with the row qf five large cusps of equal size in the middle line, and four smaller cusps on either side placed in the intermediate spaces. The last molar is quite one-sided, being formed of one large cusp, in a straight line with the large middle line of cusps in the other teeth, and three smaller ones, all on the inner side, the hinder-most forming the posterior border of the tooth. The drawings (A & B) will more readily explain the formation of the teeth of these two species. 9. ARVICANTHIS ABYSSINICUS. 2 . Laga Hardim, 15th January, 1899. 2 . Jiffa Densa, 7800 ft., 23rdJanuary, 1899. P R O C . ZOOL. Soc-1900, No. VI. 6 |
