1901.] SKULLS or LEMURS AND MONKEIS. 145 



also a fronto-maxillary suture, although of less extent. In Oal- 

 lithrico the lacrymal therefore occupies a more backward position 

 than in the preceding genera. Notwithstanding this, the crista 

 post, is generally very strong, the crista ant., on the contrary, 

 much flattened, especially in its upper region ; so that in some 

 cases — G. nigrifrons, Br. M. No. 51 c ; 0. personata, Br. M. 

 No. 45.4.2.li (PI. XII. fig. 7) and No. 51 cZ— the fossa appears 

 quite as much outside the orbit as in extreme cases of Ateles. 



NyctipitTiecus. 

 Fourteen skulls. — As described by Gregenbaur in N. trivirgatus, 

 the whole of the crista posterior belongs to the maxilla, which, more- 

 over, generally descends into the fossa. In the only skull of N. tri- 

 virgatus available (Br. M. No. 1459 h) — 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 speci- 

 mens), W. ruHpes (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 h) 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. 



PitJiecia. 



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, Lagotlirix, Chrysotlirix, and 

 Cebus, present essentially the conditions of the Simiidse. 



LagotJirix. 



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) 



Pboc. Zool. Soc— 1901, Vol. I. No. X. 10 



