1901.] SKULLS OF LEMURS. AND MONKEYS. 141 



within the fossa, and separate again ahnost immediately, so as to 

 include between each other the thin bony plate above mentioned. 



In several of the younger specimens an intercalar bone is 

 present as in Perodictims. In specimen No. B7 d (Br. M.) it 

 forms the medial continuation of the crista posterior, being 

 limited anteriorly by the maxilla — with which it begins to co- 

 ossify, — medially by the nasal, laterally by the planum, posteriorly 

 by tlie frontal. In other slightly older specimens (Br. M. No. 67 ^', 

 No. 67 c ; E. C. S. No. 290) the intercalar bone is almost completely 

 overgrown by the frontal. 



Lacryuial region of Avahis luniger, about ^ nat. size. 

 (Lettering as in text-fig. 26.) 



The malar terminates anteriorly above the interspace between 

 m. 1 and the posterior premolar. 



Nycticehus. 



In this genus (see text-fig. 41) the crista posterior appears to 

 be formed, either by the maxillary (laterally) and the frontal 

 (medially) — joining in a suture in advance of, and above, the os 

 planum, — or by two processes of the maxillary, joining in the 

 same manner. Younger specimens show an intercalar bone which 

 occupies the same position as in Perodicticus and Loris, and 

 coalesces either with the maxillary or with the frontal. In some 

 cases (N. javanicus, Br. M. No. 66 e; iV. tardigradus, Br. M. 

 No. 1550 b) a small process of the planum creeps upon the orbital 

 margin between the maxilla and the frontal, or even advances into 

 the fossa. 



There is no trace of the lacrymal within the orbit, nor, as has 

 just been stated, on the orbital margin, where it seems to have 

 been entirely covered by the maxilla, os planum, and frontal. 

 Neither can the lacrymal be traced in the groove which in front 

 of the crista posterior represents the fossa lacrymalis of other 

 Lemurs. With the exceptions before mentioned, when the planum 

 encroaches on the fossa, the bottom of the latt er is made up by 

 two processes of the maxilla, which also encircles the canalis I. in 

 front. 



The malar does not advance on the orbital margin farther than 

 above the posterior end or the middle of the posterior premolar. 



In old specimens all the sutures are obliterated. 



