1901.] SKULLS OP LEMURS AND MONKEYS. 151 



that of the Malagasy Lemurs, on the contrary, by an increase in size 

 of the pars facialis. The large expansion of the lacrymal on the 

 face and the anterior bordering of the canalis by the latter bone, 

 both characters which amongst the Prosimiae occur only in the 

 Malagasy Lemurs, are rather an exception within this group; they 

 go hand in hand with the elongation of the facial cranium 

 generally. As a rule in the Malagasy Lemurs the pars facialis is 

 of moderate size, and the anterior boundary of the fossa is provided 

 by the maxilla. In the Oriental and Ethiopian Lemurs the maxilla 

 ahvays borders the fossa to a large extent and chiefly in front ; the 

 pai's facialis is reduced to a minimum ; the pa7-s orhitalis is also 

 reduced, owing chiefly to the encroachment by the planum. In 

 two genera (Loris, Nycticebus) the lacrymal disappears entirely 

 from the outer surface of the cranium, outside and inside the orbit. 



Amongst the Platyrhinse, only in Mycetes and Ateles, and, up to a 

 certain extent, in Bracliyteles and Gallithruv, the fossa 1. shows a 

 tendency to expand upon the face ; whilst in all the other genera, 

 at the top of which are Lagothrix, Chrysothtnx, and Cebus, the 

 lacrymal remains inside the orbit. The crista anterior being formed 

 by the maxilla, the same condition as in Anthropoid Apes and 

 Man is arrived at, and, as in them, it coincides with the reduced 

 size of the facial cranium. 



In the lower Catarhinae the anthropoid condition is verified in 

 Miopithecus, Rhinopithecus (PL XI. fig. 8), and Semnopithecus, in a 

 minor degree in Colobus. In all the other genera of Cerco- 

 pithecidse — Nasalis, Cercopithecus, Cercocebus, Inuus, Macacus, 

 Oynopithecus, Papio — the condition of the lacrymal region is, as a 

 rule, further removed from that of Simiidae and Homo than in 

 the great majority of Platyrhine genera. In extreme cases, when 

 the facial region is lengthened, in these Cercopithecidse also the 

 lacrymal expands on the face and the fossa tends towards a pre- 

 orbital position. 



Summing up, and in order to arrive at a generalization, the 

 following points are to be insisted upon : — 



A great facial expansion of the lacrymal, and particularly its 

 extension beyond the fossa lacrymalis, — 



1. Does not occur, the converse being the case, in the one 



Tertiary Lemur of which the lacx'ymal region is known ; 



2. It is scarcely more frequent in Lemurs than in the higher 



groups ; the greatest reduction of the lacrymal occurs 

 precisely within the Prosimiae; 



3. It is at its minimum in young individuals ; 



4. The genera of each groap in which this character is presented 



have certainly no closer relationship with those of another 

 group ; 



5. It can always be traced back to an elongation of the facial 



cranium, necessitated by a more powerful dentition. 



The conclusion is, that a great facial expansion of the lacrymal, 

 and particularly its extension beyond the fossa lacrymalis, is, in 



