SLOTHS. 207 
The two-tced sloths, or unaus, of which there are two well- 
‘defined species, constitute the genus Cholapus, characterised 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 characters 
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. hoffmanin7) 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 
Central 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. tridactylus), Bates observes that the Indians call it ai ybyreté, or sloth 
of the mainland, to distinguish it from the B. infuscatus, which has a long black 
and tawny stripe between the shoulders, and is called ai ygapo, or sloth of the 
flooded lands. Some travellers 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 production of these silent shades, lazily moving from branch 
to branch. Every movement 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 remained, 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 occasion he saw a three-toed sloth swimming 
a river, about five hundred yards wide. 
Sloths are mainly nocturnal; and in their usual attitude they hang suspended 
back downwards. When sleeping, they roll themselves into a ball, with the 
head tucked between the arms; in this position they somewhat resemble the 
Two-Toed Sloths 
Habits. 
