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Show 96 MR. OLDEIELD THOMAS ON [Feb. 6, other in the neighbourhood of El Khaur, a place about forty miles north-east of Aden, aud some twenty-five miles west of Shukra. But, as might be expected, no definable difference is to be found in the animals of the two localities. The notes on habits &c. placed in inverted commas have been contributed by Mr. Percival. 1. PAPIO ARABICUS, sp. n.1 a. 2 • Subaihi Country, about 60 miles north-west of Aden. Alt. 1000 metres, 16th October, 1899. " The mountains run up to nearly 2000 metres, but the Baboons keep to the lower slopes." Allied, so far as can be determined from the female, to Papio hamadryas, aud therefore probably the form from Aden which has been commonly referred-though without the examination of specimens-to that species2. But this is by no means certain, and it may be that either the true P. hamadryas occurs naturally in the Aden district, or that examples of it have been brought across from Somaliland to Aden during the long-continued native intercourse between the two places, and that the Aden herd is the offspring of escaped specimens. But whatever may be the case with the herd occurring close to the town of Aden, certain it is that the present specimen, which was obtained by a native about sixty miles to the north-west, cannot be referred to the true P. hamadryas. The main difference appears to be in size, but it unfortunately happens that while the present example is a female, all the available specimens of P. hamadryas are males, so that sexual difference has to be allowed for in distinguishing the two forms. But greatly as the sexes of Baboons may differ in general size and length of skull, the dimensions of the teeth, at least of the cheek-teeth, seem almost or quite unaffected by sex. Thus of a pair, male and female, of the East-African Baboon (Papio thoth) of about the same age (the male slightly older, but both rather immature), the following are tbe respective measurements (in millim.) of the skull and teeth :- Combined lengths of Total length 5 upper cheek- 4 posterior lower Length of last ofskulh teeth. cheek-teeth3. lower molar. d .... 187 50 46 15 2 159 50 46-4 15-6 The teeth are therefore of about the same dimensions in the two sexes, in spite of the difference in the size of the animals themselves. A similar result has been found in M a n , and is, indeed, 1 Preliminary notice, P. Z. S. 1899,"p. 929. 2 See Matschie, SB. Ges. nat. Freunde, 1893, p. 25. 3 The anterior lower premolar in Baboons partakes of the sexual specialization of the canine, and has therefore to be eliminated in a comparison of this sort. |