FAMILIES OF EDENTATA. 573 



Concerning the skeleton we may note the single set of | rootless, un- 

 enamelled teeth, the incomplete zygomatic arch with a descending 

 process from the jugal, the presence of clavicles, the rod-like appearance 

 of the embryonic stapes, the occurrence of nine cervical vertebrae in 

 Bradypus, of six in Cholcepus. 



As in most herbivorous animals, the stomach is complex, but there is 

 no csecum. In the limbs the main blood-vessels break up into nu- 

 merous parallel branches. The uterus is simple, the vagina seems to 

 be originally divided by a median partition, the placenta is a deciduate 

 dome-shaped disc. One young one is born at a time. 



\i.. Megatheriidce or Ground-Sloths — extinct forms of large size, inter- 

 mediate between the sloths and the ant-eaters. Their remains 

 are found in Pleistocene deposits in N. and S. America. 

 The genus Megatherium exceeded the Rhinoceros in size. 



3. Myrmecophagidse — the ant-eaters, t oothle ss, hairy animals, literally 



Edentate, with long thread-like protrusible tongues viscid with 

 the secretion of greatly enlarged submaxillary glands. One 

 form, Myrmecophaga jubata , is terrestrial, the others belonging 

 to the genera Tamandua and Cycloturus are arboreal. All 

 feed on insects. All are Neotropical. The skull is long ; the 

 third finger is greatly developed, the others are small ; the pes 

 has four or five almost equal, clawed toes ; the clavicles are 

 rudimentary ; the tail is long and sometimes prehensile. The 

 brain is well convoluted. The uterus is simple. The placenta 

 is dome-like or discoidal. 



4. Dasypodidae — the armadillos, all S. American except Tatusia 



novemcincta, which extends as far north as Texas. They are 

 nocturnal, omnivorous animals, able to run and burrow rapidly. 

 They are unique among living mammals in having a dermal 

 armature of bony scutes united into shields and rings, and 

 covered by horny epidermis. The teeth are numerous, simple, 

 of persistent growth, and in most cases of one set. Clavicles 

 are well-developed. The digits have strong claws or nails. 

 The brain has large olfactory lobes ; the cerebral hemispheres 

 have few convolutions. The tongue is long and protrusible, 

 and the submaxillary glands are large. The stomach is 

 simple. The uterus is simple. The placenta is discoidal 

 and deciduate. 



Examples ; — Dasyptis, Chlamydophorus, Tatusia. 



5. Glyptodontidse — extinct Pleistocene types, mostly S. American, 



but represented in Mexico and Texas. The body was often 

 huge, and was covered by a solid carapace of great strength. 

 "Why such a form as the Glyptodon should have failed to 

 keep his ground is a great mystery ; nature seems to have 

 built him, as Rome was built, for eternity." (W. K. Parker.) 



6. Manidsa — the Ethiopian and Oriental Pangolins, covered dorsally 



with overlapping horny scales. They are terrestrial, burrowing 

 animals, but sometimes climb trees. They usually feed on 

 termites. There are no teeth, the tongue is long and pro- 

 trusible. The uterus is bicornuate, the placenta diffuse and 

 non-deciduate. There is one extant genus Manis. 



