76 



THE MANUS. 



[chap. 



r-\ 



moderately elongated and flattened phalanges, which are 

 never increased in number beyond the limit usual in the 

 Mammalia. 



Among the animals constituting the 

 Order Edentata there is great diversity 

 in the structure of the fore-foot. They 

 agree, however, in wanting an os central e, 

 and (with the exception of Mam's) in the 

 presence of distinct scaphoid and lunar 

 bones. 



In the existing Sloths the whole manus 

 is long, very narrow, habitually curved, and 

 terminating in two or three pointed, curved 

 claws, in close apposition with each other, 

 incapable, in fact, of being divaricated, so 

 that it is reduced to the condition of a 

 hook, by which the animal suspends itself 

 to the boughs of the trees among which 

 it lives. 



The carpus is small, and articulates by 

 a smooth rounded surface with the lower 

 end of the radius. In the Three- toed 

 Sloths (genus Bradypiis) it consists of 

 distinct scaphoid, lunar, and cuneiform bones in the first 

 row, but usually of only two bones in the second row, the 

 unciform, and a connate magnum and trapezoid, the trape- 

 zium being generally ankylosed to the rudimentary first 

 metacarpal.^ There is a small rounded pisiform, but no 

 radial sesamoid. The first and fifth metacarpals are present 

 in a rudimentary condition, but bear no phalanges. The 

 three middle digits are nearly equally developed. The 

 proximal phalanges are extremely short, and become soon 



1 See Journal of Anatomy and Physiology, vol. vii. p. 255. 



Fk;. ICO. — Bones of the 

 risht manus of the 

 Two-toed Sloth {Cho- 

 lapus didactyius). 5. 



