430 DR. J. E. GRAY ON THE BRADYPODIDE. [May 2, 



has the brown tint of the figure of Bradypus torquatus, Illiger, 

 represented in Wagner's ' Supplement to Schreher's Saugthiere,' 

 tab. lxiv. a. 



2. Bradypus affinis. 

 Skull rather convex between the orbits. 



Bradypus affinis, Gray, P. Z. S. 1849, p. 68, t. x. f. 2 (skull) ; Cat. 

 Edentata B. M. p. 364. 



Arctopithecus. 



Pterygoids compressed, crest-like, solid. Males with a patch of 

 soft hair between the shoulders not found in the females. Inter- 

 maxillary bone rhombic, with an attenuated process behind. Tbe 

 front of the lower jaw broad and truncated, sometimes with a slight 

 keel in the centre near the upper margin. The front grinders are 

 short and blunt. The upper process of the malar bone attenuated. 



Arctopithecus, Gray, P. Z. S. 1849, p. 69 ; Cat. Edentata B. M. 

 p. 364. 



The hinder angle of the lower jaw differs very considerably in 

 shape, as I showed in the ' Proc. Zool. Soc' 1849, t. xi. f. 1, 3, 

 4, 5, 6. The sutures between the bones of the face are often distin- 

 guishable in well-developed skulls, which evidently belong to full- 

 grown animals. 



In the two preceding genera no difference has been observed be- 

 tween the colour of the males and the females ; but from numerous 

 observations that have been made upon specimens of this genus I 

 think that it may now be established that the males are ornamented 

 differently from the females — that is to say, that they have a patch of 

 soft short hair between the shoulders, which is generally of a more 

 or less orange-colour, and in one species pure white. The females, 

 on the contrary, are destitute of this mark. Both sexes generally 

 have a more or less distinct black dorsal streak and abundant soft 

 under-fur which agrees in colour with the long hair above it. 



As this difference of the colouring of the sexes has produced various 

 opinions, and sometimes caused the sexes of the same animal to be 

 regarded as distinct species, I have given a resume of the various 

 ideas on the subject, and of the characters that have been given of 

 the species by the authors who have studied the whole genus. 



Buffon (Histoire Nat. xiii. 1765, p. 60), in his account of the Ai, 

 figures what he calls the " jeunes Ai's " (tab. v.), which are probably 

 young females, and "i'A'iadulte" (tab. vi,), which is evidently a 

 male. Daubenton in his description calls this the first specimen, 

 and observes that he gives to it the name of " Ai' de dos brule, parce 

 qu'il semble que son poil ait ete en effet bride sur la dos." This 

 is evidently the male of A. blainvillei ; for he says the head and neck 

 are covered with long flexible brown-black hair ; and the young (the 

 second), he says, chiefly differs from the former by the face being 

 surrounded by yellowish and the head and neck blackish ; there- 

 fore it is difficult to say whether it is the female of Bradypus 



