BRA D YPODID^E \ 8 1 



trees of their native forests abound ; the concealment thus afforded 

 being heightened in some species by the peculiar greenish tint 

 of the outer covering very uncommon in mammals. This is not 

 due to the colour of the hair itself, but to the presence upon its 

 surface of an alga, the lodgment of which is facilitated by the fluted 

 or rough surface of the exterior of the hair, and the growth of which 

 is promoted by the dampness of the atmosphere in the gloomy 

 tropical forests, as it soon disappears from the hair of animals kept 

 in captivity in England. Sloths are nocturnal, silent, inoffensive, and 

 solitary animals, and usually produce but one young at birth. They 

 appear to show an almost reptilian tenacity of life, surviving the 

 most severe injuries and large doses of poisons, and exhibiting 

 longer persistence of irritability of muscular tissue after death than 

 other mammals. 



In the Bradypodidce,, as well as in the Myrmecophagidce, the 

 testes are placed close to each other, lying on the rectum between 

 it and the bladder ; the penis is quite rudimentary, consisting 

 of a pair of small corpora cavernosa, not directly attached by their 

 crura to the rami of the ischia, and having a glans scarcely larger 

 than that of the clitoris of most mammals, and, as in birds and 

 reptiles, without any true corpus spongiosum. In the females of 

 both families the uterus is simple and globular ; and the vagina, at 

 least in the virgin state, is divided into two channels by a strong 

 median partition. The deciduate placenta of Ckofaptu is composed 

 of a number of lobes aggregated into a dome-like mass : and it 

 does not appear that the placenta of the Anteaters departs in any 

 important characters from this type. According to the late Pro- 

 fessor W. K. Parker, the embryos of the Sloths, Anteaters, and 

 Pangolins have the stapes of the middle ear in the form of a rod, 

 thus showing affinities with a very primitive type of mammalian 

 organisation. 



The Sloths were all included in the Linnsean genus Bradypus, 

 but Illiger very properly separated the species with but two claws 

 on the fore feet, under the name of Cholcepus, leaving Bradypus 

 for those with three. 



Bradypus}- Three-toed Sloths. Teeth usually |- on each side ; 

 no tooth projecting greatly beyond the others ; the first in the 

 upper jaw much smaller than any of the rest ; the first in the 

 lower jaw broad and compressed ; the grinding surfaces of all much 

 cupped. Vertebrae : C 9, D and L 20 (of which 15 to 17 bear ribs), 

 S 6, C 1 1 . All the known species present the remarkable pecu- 

 liarity of possessing nine cervical vertebrae, i.e. nine vertebrae 

 in front of the one which bears the first thoracic rib (or first 

 rib connected with the sternum, and corresponding in its general 

 relations with the first rib of other mammals) ; but the ninth. 

 1 Linn. Syst. Nat. 12th ed. vol. i. p. 50 (1766). 



