182 



THE EDENTATES. 



number of the neck vertebra, which is so 

 constant in almost all other mammals, varies 

 in the sloths. Instead of seven a species 

 closely allied to the unau or two-toed sloth 

 has only six; the ai or three-toed sloth has 

 nine. In general the skeleton of the sloths 

 is distinguished by great power of move- 

 ment in the joints; many of the vertebrae 

 resemble those of serpents, and this structure 

 enables the animals to take up the most sin- 

 gular attitudes with the greatest ease, and to 

 perform gyrations and dislocations which 

 would be impossible for other mammals. 

 The tail, which is composed of broad vertebrae, 

 is either short or even quite imperceptible. 

 The body is covered with a coat of long, 

 coarse, stiff hair, so that the animal when 

 crouched up appears like a bundle of hay or 

 dried moss. The direction of the hair is from 

 the ventral towards the dorsal surface, in ac- 

 cordance with the inverted position which 

 these animals so frequently assume. The 

 teeth are simple, without roots, and in both 

 jaws are set so far apart from one another 

 that those of the one jaw fit into the gaps left 

 between those of the other. They usually 

 get worn away by use into obliquely placed 

 transverse ridges. All the teeth are set in 

 the maxillae or mandibles; the premaxillse are 

 quite rudimentary. The stomach has three 

 parts like those of the peccaries; there is a 

 paunch and a reticulum with large cells. The 

 oesophagus is continued in the form of a 

 groove to the pyloric region of the stomach. 

 With respect to the sexual organs the sloths 

 stand very near the monotremes and marsu- 

 pials, but there are teats on the breast. 



The sloths are peaceable, sluggish animais, 

 and lead an essentially nocturnal, arboreal 

 life in the primeval forests of South America. 

 They are usually seen singly or in pairs, with 

 head and back downwards, hanging from the 

 branches of trees, to which they cling with 

 two feet, or frequently with only one. Not 

 uncommonly these animals will remain by the 

 hour in the most curious positions without 



moving. They move along slowly from 

 branch to branch, and never leave a tree 

 till they have entirely stripped it of its leaves 

 and fruit. By night they become, indeed, 

 a little more active, but even then their 

 movements are slow and deliberate. They 

 get from one tree to another by hooking on 

 to an adjacent branch, without descending 

 to the ground, where their mode of progres- 

 sion is extremely toilsome; in walking they 

 seem as if mowing with their legs. Sloths 

 can endure hunger and thirst for a long time, 

 but not cold. They bring forth only one 

 young one at a birth. Immediately after birth, 

 the young sloth hangs on to the neck of the 

 mother, who carries it about with her. Indo- 

 lent and stupid, the sloths cling with unparal- 

 leled strength to their branches, and defend 

 themselves by their apathy. Nevertheless it 

 has been found possible to domesticate sloths 

 so far that they could recognize the voice of 

 their keepers who brought them their food. 

 But this is all that can be attained. The 

 food is conveyed to the mouth by means of 

 the fore-paw. 



The AY or Three-toed Sloth (Bradypus tri- 

 dactylus), which is represented in a full-page 

 illustration (PI. XXXVIII.), has three claws 

 on all the feet; its neck is cylindrical and 

 rather long, the head spherical and of uniform 

 thickness. The nose is a little turned up. 

 The nearly black face with white rings round 

 the eyes is quite naked. The coarse dry 

 brittle hair begins on the brow, is parted on 

 the back, and forms a ring or collar round 

 the face, to which the small eyes, without 

 apparent pupils, impart a stupid and at the 

 same time rather childish look. The tail is 

 short, measuring in an animal of about 20 

 inches in length only 2 inches or less. There 

 are five teeth in each half of each jaw, the 

 first being a little smaller than the others; 

 the chewing surface is round and concave. 

 The colour is usually a fallow gray with two 

 light brown but not very conspicuous stripes 

 along the back. The ai lives in Brazil. 



