112 EDENTATA. 



SECTION XVIII. 

 FIFTH ORDER, EDENTATA. (Lat. toothless.) 



This name was originally given by Cuvier, to the animals of 

 this order, from their agreement in the absence of incisive teeth 

 from their jaws, and in the length of their claws. Apart from 

 this agreement, they appear to have among themselves but little 

 natural affinity. To several of the ant-eating tribe, which this 

 order includes, the name Edentata is literally applicable ; but in 

 other genera it is limited to the front, or incisor teeth. In this 

 order Cuvier included the Monotremata, but their most natural 

 place seems to be with the Marsupials. 



I. Family, TARDIGRADA, (Lat. tardus, slow, gradior, to step;) 

 also named Bradypodidae, (Gr. Ggadvg, bradus, slow, novg, pous, a 

 foot.) This includes two genera, Bradypus tridactylus, (Lat. 

 three-toed,) the Ai, or SLOTH, and Choloepus, (Gr. /wlo?, cholos, 

 lame, novg, pous, a foot,) didactylus, (Lat. two-fingered ;) the 

 UNAU. 



These animals have no incisor teeth, four canines, two in each 

 jaw, fourteen molars, eight in the upper and six in the lower jaw. 

 The molar teeth consist each of a cylinder of bone, covered with 

 enamel ; hence their surfaces are always concave, the enamel 

 wearing less rapidly than the soft interior. No laminae, or folds 

 of the enameled substance penetrate the body of the teeth, as in 

 most other animals ; the canines are somewhat longer than the 

 molars, and in form pyramidal. When these animals stand 

 erect upon their hind legs, their fingers can reach to the ground ; 

 and when moving upon all fours, they trail themselves slowly 

 and painfully along upon their elbows. Their claws surpass the 

 whole foot in length, and are very sharp and crooked. (See Plate 

 VI. fig. 5.) In a state of rest, they are drawn down upon the palm 

 and wrist, and can be extended only by the will and muscular effort 

 of the animal. Sharp, and bent in form, they are so many effective 

 hooks for holding on; while the rigidity of the limbs gives a firm 

 hold ; the feet and thighs are jointed obliquely, which adapts them 

 for embracing a branch ; and the great length of the arms aids 

 these animals in seizing a fresh hold, and drawing twigs and 

 leaves, their usual food, to their mouths. They are born and live 

 on the trees, and never leave them, unless from the operation of 

 force, or accident, resting not upon the branches, like the squirrel, 

 or monkey, but under them, and moving and even sleeping sus- 



