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Show 144 MR. O. THOMAS ON T H E [Feb. 20, Mammal discovered during Mr. Johnston's exploration of the Nyasa Fauna, I have named in his honour, is remarkable as being the only member of the genus distinguished by any colour-markings other than those of the dorsal spot. The prominent black earmark is in fact quite unique in the group, while its reddish-brown crown, although sometimes present in P. abyssinica, will readily distinguish it from its nearest ally, P. capensis, in which the crown is finely grizzled like the back. The unusual massiveness of the grinding-teeth will also readily separate P. johnstoni from all other forms. The occurrence of this peculiar but clearly representative species between the ranges of P. capensis and P. shoana tends to confirm their distinctness from each other, on which I had thrown some doubt when writing in 1892. Since my monograph of the genus was prepared, two species of Procavia have been described by Dr. Matschie1, but both belong to the Dendrohyrax group, and have therefore nothing to do with P. johnstoni. 25. PROCAVIA BRUCEI, Gray. a, b. Ad. & imm. sks. $ . Mpimbi, Upper Shire. 4/93. c Yg. sk. Port Lister, 3500 ft. 25/7/93. These specimens probably represent Hyrax mossamhicus, Peters. The youngest of them has already got its interparietal sutures closed. The basal lengths of the three skulls are :- a. (Stage VIII.), 79 mm.; b. (Stage V.), 71 ; c. (Stage III.), 63. The ears of these examples are more prominently white than is usual in P. brucei, and their bellies and feet are also particularly white, characters in which they somewhat resemble the closely allied P. bocagei, and it is probable that when more specimens of the latter are obtained the two forms will be found to grade into one another. In looking at the fine set of Dassies from Nyasa now sent, three of P. johnstoni and three of P. brucei, all found more or less together, one cannot fail to be struck by the peculiar method in which evolution seems to have been going on in the group. Not only do they afford a striking instance of the remark made previously 2 as to the constant occurrence together of one species of the hypsodont and one species of the brachyodont group, the competition between members of the two groups apparently not being severe enough to prevent their living together, but also, the practicability of their living together being once proved, they seem then to have tried to become as different from each other in their superficial characteristics as possible. Thus, while the hyposodont P. johnstoni is distinguished from its allies of the same group by its dark head, black ear-markings, dirty yellow belly, and black 1 S.-B. nat. Fr. Berl. 1892, p. 110, and 1893, p. 112. 2 P. Z. S. 1892, p. 57. |
