Mammalia: Classification 743 



(see p. 46). Teeth entirely lacking in adults of some members of 

 Order. Claws usually very long, curved, and strongly developed. Brain 

 of primitive type. 



The Order includes the tree sloths, South American anteaters. 

 and the armadillos. 



Modern sloths are arboreal, but their arboreal habits are unique. 

 Most arboreal mammals are especially nimble — e.g., squirrels and 

 monkeys. The sloths (Fig. 552), ranging in size from that of a small cat 

 up to four or five times the bulk of a cat, are short in the body and long 

 in the legs. Hooking the strongly curved claws of its long digits over 

 the branch, the animal suspends itself beneath it and, in this upside- 

 down attitude, clambers about slowly and clumsily amid the foliage 

 which is its food. On the ground it is capable of only an awkward 

 crawling gait. The hair is long, coarse, and gray, but becomes more or 

 less infested by an alga which gives it a greenish tint which may have 

 some protective significance. The teeth consist of four or five cheek- 

 teeth (the most anterior possibly canine) in each half-jaw. The three- 

 toed sloth (Bradypus) has nine cervical vertebrae; the two-toed 

 sloth (Choloepus) has only six cervicals. 



The anteaters (or antbears: Fig. 553) are hairy, some of them 

 quite long-haired, especially as to the tail. They have the usual adapta- 

 tions for their peculiar diet — long narrow snout, long sticky tongue, 

 and forefeet equipped for digging out ants or, more commonly, ter- 

 mites. The adults are literally "edentate." Best known are the "great 

 anteater'* 1 (Myrmecophaga), whose length from tip of snout to tip 

 of tail may be 7 feet, and the "lesser anteater" (Tamandua). Some 

 of the smaller anteaters are arboreal and the long tail is prehensile. 



The armadillo (Dasypus and other genera: Fig. 554) simulates a 

 reptile in its armor of heavy dermal bony plates overlaid by horny 

 scales, but stiff coarse hairs projecting between scales betray the 

 mammal. The plates in the region of the trunk are usually small and 

 squarish and arranged in transverse bands whose number varies 

 among the several species. Large plates may occur dorsally in the 

 regions of the shoulder and sacrum. Cheek-teeth are numerous — 

 usually 8 to 10 in each half-jaw, but in the giant armadillo (Prio- 

 dontes) the number may reach 25, thus greatly exceeding the usual 

 number in placental mammals. 



Armadillos range in size from that of a rat to a length, including 

 tail, of 4 or 5 feet. They are burrowing and nocturnal in habit, chiefly 

 insectivorous or sometimes carnivorous, and not averse to eating long- 

 dead carcasses. 



In at least some armadillos there is an extraordinary feature of 

 reproduction. The animal usually bears four young at a time, which 



