Zoological Society. 233 



This species, of which we have four specimens of different ages in 

 the Museum, is easily known by the length, very loose and flaccid 

 nature of its hair, and the indistinctness of its markings. The black 

 on the back appears to arise from the hair of the shoulders being 

 worn away. Three, of very different ages, are pale grey-brown, 

 with a short, broad, blackish streak between the shoulders, and 

 have the rump and each side of the dorsal streak more or less white, 

 and an indistinct whiteness on the outer side of the upper arms. 



Buffon's description of his second specimen of Ai agrees better with 

 this species than with any other which has come under my observation. 



Prince Maximilian gives a good figure of the female and young of 

 this species. He observes, " Les males a de chaque cote du dos une 

 ligne longitudinale blanche" 



In the British Museum there is a specimen about half the size of 

 the largest of the former, which is very like it in the flaccid nature of 

 its fur, but the whole upper part of the body is pale whitish grey, 

 with two or three indistinct white spots on the sides, and there is a 

 short black streak edged with a white spot of soft hair on each side 

 between the shoulders. This was brought from Venezuela by Mr. 

 Dyson. 



There is another specimen rather smaller than the former, and like 

 it in colour and appearance, but it has no indications of the back streak 

 or white soft hair on the shoulders. Brought from Para by my son- 

 in-law, Mr. J. P. George Smith. 



I am by no means certain that these specimens may not be indica- 

 tions of the existence of other species, which can only be proved by 

 the comparison of more specimens. 



Besides these species of which we have skins and skulls, there is in 

 the British Museum the skeleton of a species of this genus, which was 

 sent from Para by my son-in-law, which differs essentially from all 

 those before described, both in the greater length of the head and in 

 the form of the hinder edge of the lower jaw, and which I have there- 

 fore indicated under the name of 



5. Arctopithecus problematicus. 



Fur unknown. Skull rather elongate ; forehead broad, rather con- 

 vex on each side over the middle of the orbit. 



Lower jaw with a broad rather produced angle, bent up at the tip 

 and regularly rounded beneath, and with a distinct angular keel up 

 the symphysis, rendering the upper edge angularly produced. 



Hab. Para ; J. P. George Smithy Esq. 



The keel in the lower jaw is similar to that of A. Blainvillii, but 

 the angle is much more produced. In the form of this part it most 

 resembles that which I have considered as the young of A. Jlaccidus ; 

 but the angle is much broader and more recurved, and it differs from 

 both skulls of that species in the skull, and especially the lower jaw, 

 being much more elongated behind compared with the length of the 

 tooth -line. 



