1378 THE EDENTATES 



that a captive specimen, when dragged from the branch to which it was clinging, 

 uttered a shrill scream. 



The two-toed sloths, or unaus, of which there are two well-defined 

 W( qi th species, constitute the genus Cholcepus, characterized by having only 

 two functional toes on the fore-foot; these two digits representing the 

 index and middle finger of the human hand. The hind-foot has, however, three 

 toes, as in Bradypus. The unaus are further distinguished by the characteristics of 

 their teeth; the first pair in each jaw being longer and stouter than the others, from 

 which they are separated by a considerable interval. These anterior teeth assume, 

 indeed, the characters of tusks, and have their summits obliquely worn away by 

 mutual attrition. That they do not correspond to the true tusks, or canines of other 

 Mammals is shown, however, by the circumstance that the lower ones bite behind, 

 instead of in front of those of the upper jaw. In the common unau (C. didactylus) 

 the number of vertebrae in the neck is the usual seven, but in Hoffmann's sloth (C. 

 hoffmanni) it is reduced to six. Of these two species the former is restricted to 

 Brazil, while the latter extends from Ecuador to Costa Rica. Hoffmann's sloth 

 utters at rare intervals a cry like the bleating of a sheep, while when suddenly 

 seized it gives vent to a loud snort. 



The haunts of the sloths are the primeval forests of South and Cen- 

 tral America, where vegetation attains its highest development, and 

 the warm air is heavily laden with moisture. The darker and denser the forest, the 

 more thickly is it tenanted by these creatures, which are as thoroughly arboreal as 

 the squirrels and spider-monkeys, and seldom or never descend of their own accord 

 to the ground. Indeed, on the ground the sloth is but a helpless creature, walking 

 uneasily on the edges of its in-turned feet, and seeking as soon as possible to regain 

 its native trees. Writing of the habits of the common three-toed sloth (B. tridacty- 

 lus), Bates observes that the Indians call it ai' ybyrete, or sloth of the mainland, to 

 distinguish it from the B. infuscatus, which has a long, black and tawny stripe be- 

 tween the shoulders, and is called ai' ygapo, or sloth of the flooded lands. Some 

 travelers in South America have described the sloth as very nimble in its native 

 woods, and have disputed the justness of the name which has been bestowed upon it. 

 " The inhabitants of the Amazon regions, however, both Indians and descendants 

 of the Portuguese, hold to the common opinion, and consider the sloth as the type 

 of laziness. . . . It is a strange sight to watch the uncouth creature, fit pro- 

 duction of these silent shades, lazily moving from branch to branch. Every move- 

 ment betrays, not indolence exactly, but extreme caution. He never loosens his 

 hold from one branch without first securing himself to the next, and when he does 

 not find a bough to immediately grasp with the rigid hooks into which his paws are 

 so curiously transformed, he raises his body, supported on his hind-legs, and claws 

 around in search of a fresh foothold." Bates goes on to say that after watching its 

 movements for some time, he shot the specimen under observation; its body re- 

 mained, however, firmly suspended to the bough to which it was clinging, and it 

 was not till the muscles became relaxed that it fell. He adds that on another oc- 

 casion he saw a three-toed sloth swimming a river, about five hundred yards 

 wide. 



