1871.] DR. J. E. GRAY ON THE BRADYPODIDjE. 431 



of skulls. In five of them (7366, young, 736a, 607, 910, and 736«*) 

 they are separated from each other by a space of considerable width. 

 This space is much narrower behind in 151 Oe, which is a much older 

 skull than any of the others. In three skulls (1510a, 1510) from 

 Costa Rica, both of which are young, the temporal muscles are only 

 separated by a very narrow ridge for about half or three-quarters of 

 an inch; in an adult skull, that wants its hinder part (1510), they 

 appear to approximate much further forward, but the occipital part 

 of the skull is deficient. 



The malar bones are very different in shape in the different spe- 

 cimens : in some the descending bone is very broad and fan-like, and 

 in others it is comparatively small ; the ascending one varies much 

 in length, but is generally short, not reaching the zygomatic pro- 

 cess and squamosal ; but in one specimen from Costa Rica it nearly 

 reaches the process, to which it is united by a cartilage. 



There is a great difference in size, shape, and vesicularity of the 

 pterygoids, and also in the substance, some being very thin and others 

 thick and hard. 



1. Cholcepus. 



1. Cholcepus didactylus, Gray, P. Z. S. 1849, p. 65 j Cata- 

 logue, p. 363 ; Wagn. Suppl. vol. iv. p. 158. 



One, which is generally dark, has the end of the hairs of the occi- 

 pital crest white, and more or less tinted with bright green. 



A young specimen received from Mr. Salvin is covered with short 

 woolly hair, of a dark brown colour, rather paler on the rump, much 

 paler on the head, the cheeks and chin, the band across the nose, 

 and the orbits being dark brown. 



All these specimens have pale, whitish claws, while the claws of 

 the other species are of a dark brown or blackish colour. 



Dr. Peters says the C. didactylus has long and C. hoffmanni short 

 claws, but I cannot see any difference in the length of the claws in 

 the Museum specimens of the two species. The claws are short in 

 the young specimens, and become longer as they increase in age. 



There is an adult specimen in the British Museum, presented by 

 Captain Kellett, of H.M.S. 'Herald,' without any special habitat, 

 which agrees with Mr. Salvin's specimens in having very long hair 

 and white claws, but is of a nearly uniform dark brown colour, rather 

 paler on the head, and redder beneath. The hair of the middle of the 

 back and of the cervical crest has more or less long white tips ; and 

 these tips of the hairs of the cervical crest have a decided green tint. 



The specimens of this genus appear to be very variable in colour 

 and in length of hair. 



A specimen said to have come from Juan de Fuca, received from 

 the Haslar Hospital, has short hair of nearly uniform length, and is 

 of a uniform dark brown colour, with scarcely any indication of an 

 occipital crest. 



Two specimens from Brazil are like the former ; but the hairs 

 are longer, and the colour is rather paler, and there is a more de- 

 cided nuchal crest. 



