OCR Text |
Show 552 MR* O. THOMAS ON THE [May 3, crowded together in the front part of the sole. The extreme of this suppression is represented by the Common Jerboa {Dipus jaculus), which has only one hind foot-pad ; Gerbillus has four, all close together at the roots of the toes ; and Zapus (the North-American " Jumping-Mouse ") has five. The members of these genera are all well known constantly to rest on the front part of the hind foot, and not to be in any way plantigrade, as are the Muridse with six well-developed hind foot-pads ; we are therefore, I think, justified in considering the Metad as showing the commencement of a similar differentiation, which, however, has not gone nearly so far as in the others. Mus Blanfordi has its foot-pads rather crowded together in the front of the foot; so that it is possibly also rather 'ess plantigrade than usual. As to the affinities of this animal (which seems to be somewhat isolated from the other Indian species), it may be seen by the synopsis on p. 531, that the only character, apart from size, by which to separate the Rats from the Mice is the very different shape of the sixth hind foot-pad ; and therefore the rudiment of this pad, mentioned above as occurring in one of our specimens, will be of service to us. This rudiment is very nearly circular ; and therefore, as far as we can rely on any one character, even though nearly universal in its application, we may, for the present, consider Mus mettada a large Mouse rather than a small Rat. Subgenus LEGGADA. Leggada, Gray, Charlesw. Mag. N. H . i. p. 586 (1837). Nannomys, Peters, Monatsh. Acad. Berl. p. 480 (1876). First upper molars with an extra cusp on their front edge (see Plate LI. figs. 10, 11). Fur more or less spiny. HaB. India and Africa. This subgenus was founded by Gray on his L,eggada Buduga, and was also stated to include Bennett's Mus platythrix. It has hitherto been considered to be confined to India; but Dr. Peters's careful description of his subgenus Nannomys shows most conclusively that it is identical with Leggada ; in fact, his characters are the very same as Dr. Gray's, except that he lays rather more stress on the presence of spines in the fur. The types of Mus minutoides, Smith1, from South Africa, preserved in the British Museum, certainly belong to this subgenus; and so, with Dr. Peters's two species, M. minimus'2 from Mozambique, and M. setulosus3 from the Cameroons, we have three species of Leggada recorded from Africa ; and there is no doubt that more still remain to be described when that continent is further explored. Sonic of the African species already described will probably also turn out to be members of this subgenus. The presence of this form in Africa was quite to be expected, 1 S. Afr. Quart. Journ. ii. p. 157 (1835). ? Reise nach Mossambique, p. 153 (1852). 3 Monatsb. Ak. Berl. 1876, p. 480. |