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Show 1901.] SKULLS OF LEMURS AND MONKEYS. 145 also a fronto-maxillary suture, although of less extent. In Cal-lithrix the lacrymal therefore occupies a more backward position than in the preceding genera. Notwithstanding this, the crista jwst. is generally very strong, the crista ant., on the contrary, much flattened, especially in its upper region; so that in some cases-C. nigrifrons, Br. M . No. 51 c; C. personata, Br. M. No. 45.4.2.11 (PI. XII. fig. 7) and No. 51 d-the fossa appears quite as much outside the orbit as in extreme cases of Ateles. Nyctipithecus. Fourteen skulls.-As described by Gegenbaur in N trivirgatus, the whole of the crista posterior belongs to the maxilla, which, moreover, generally descends into the fossa. In the only skull of N. trivirgatus available (Br. M . No. 1459 b)-in a second skull of this species the sutures are obliterated-the antero-superior angle of the lacrymal advances so far forwards, that the maxillary becomes separated from the frontal, and a lacrymo-nasal suture is brought about. The same occurs in two skulls of Nyctipithecus sp. (Br.M. No. 97.10.3.8 and No. 92.2.18.1), in the latter of which the suture between the two bones is chiefly due to the breadth of the nasal in this place. In all other skulls-N. felinus (seven specimens), N rufipes (one), N. sp. inc. (two)-the frontal and maxillary join between the lacrymal and nasal, so as to form a comparatively broad fronto-maxillary suture. Brachyurus. Three skulls of B. calvus.-The conformation of the lacrymal is on the whole similar to that of the preceding genus. The crista anterior of the maxilla forms the lower orbital margin and the anterior boundary of the fossa. In one skull (Br. M. No. 806 b) the lacrymal extends its antero-superior angle towards the nasal, which, in its turn, sends backwards a process, so that- on the left side-lacrymal and nasal join each other. Pithecia. Seven skulls.-Similar to the preceding genus. In two cases, viz. P. leucocephala (Br. M . No. 66.8.6.1) and P. sp. (Br. M. No. 1294 a), the lacrymal forms the upper margin of the fossa and at the same time joins the nasal anteriorly. The remaining genera of Cebidae, Lagothrix, Chrysothrix, and Cebus, present essentially the conditions of the Simiidse. Lagothrix. Twenty-two skulls.-The lacrymal fossa is decidedly within the orbit. The whole of the crista anterior is formed by the maxilla, forms the orbital margin, and, moreover, descends into the fossa. In a few cases the antero-superior angle of the lacrymal advances on the facial region, but only once (L. sp., Br. M . No. 0.11.5.17) PROC. ZOOL. Soc-1901, VOL. I. No. X. 10 |