208 



duction which Mr. Gray points out in his paper on the genus Bra- 

 dypus : it is much deepened behind, rendering the lower outhne 

 very convex. And further, there are certain characters pointed out 

 by Cuvier in the ' Ossemens Fossiles ' which appear to be constant, so 

 far as I have been able to observe, as it is only in young specimens 

 that the sutures are discernible. They are, first, that in this species, 

 the Ai a collier, the nasal bones are bevelled towards the middle pos- 

 teriorly, so that they form a point between the frontals, while in the 

 other species they are bevelled in the opposite direction, the frontals 

 descending between their extreme points. Secondly, that the pala- 

 tine bone forms but a narrow slip within the orbit, and the alisphenoid 

 bone occupies a much larger portion of the temporal fossa than in 

 the other species. 



The skull spoken of by Mr. Gray as being taken from a skin, pre- 

 sents characters intermediate between the other one and that upon 

 which the B. affinis is founded, therefore I refrain from inserting the 

 latter as a species until further evidences are obtained. 



Arctopithecus, Gray. 



Intermaxillary bones short and small ; postorbital process slightly 

 developed ; malar bone with the frontal and zygomatic processes 

 slightly marked, or the former wanting, the supratemporal process 

 rising obliquely ; pterygoid bones compressed and simple ; crota- 

 phite impression extending to very near the occipital ridge ; tympa- 

 nic bone well-developed, inflated ; lower jaw with its inferior outline 

 concave posteriorly, its condyle elevated ; teeth ~^, simple, rounded, 

 the anterior ones similar, small in the upper jaw. 



A. GULARis. At a dos bruU. 



A broad patch of soft yellow hair between the shoulders, and a 

 black line running through it down the back ; the upper anterior 

 molars proportionally larger, and the second less, than in the fol- 

 lowing species; the occiput again affords us a very good distinction, 

 as it is much wider and not so deep as in the following species, and 

 the foramen magnum not so large. Two skulls in the British Museum 

 present these characters, and evidently belong to adult, probably 

 aged, individuals ; that of the skeleton, also from Bolivia, seems 

 referable to the other species. 



A. MARMORATUS. 



Fur everywhere more or less lengthened, no yellow spots, dorsal 

 line grey brown ; anterior upper molars very small, the next rather 

 larger than those which follow ; occiput deeper and narrower than 

 in the preceding species, its foramen larger. 



The A. Blainvillii is not distinguishable by external markings, and 

 the skulls bearing that name in the Museum collection all present a 

 general robustness, such as age and sex might very probably occasion. 

 One of them, which, from retaining some of the sutures, seems to be 

 younger than the others, has the frontal bones less swollen, and the 



