1290 CLASS MAMMALIA. 



present, are devoid of enamel, are never developed at the extremi- 

 ties of the jaws in the situation of the incisors of other Mammals, 

 and are always homceodont and grow from persistent pulps ; while, 

 with the exception of one genus of the Dasypodidce, they are like- 

 wise monophyodont. It has, however, been recently observed by 

 Dr Ameghino that enamel was present in the teeth of certain South 

 American fossil forms ; while in the genus Diadomus, from those 

 deposits, a pair of canine-like teeth occur in the symphysis of the 

 mandible. In many of the genera the teeth are simply cylindrical, 

 but they may be transversely ridged, and occasionally they have a very 

 complex internal structure. Not unfrequently the maxillary bone 

 sends down a large descending process in the zygomatic arch (fig. 

 1 163 bis); and certain members of the order are remarkable as being 

 the only known Mammals which develop a bony exoskeleton. The 

 cervical vertebrae are short and wide, with nearly flat terminal faces 

 to their centra. 



The distribution of the Edentates is very restricted. In Europe 

 neither at the present day nor in past times is there any known re- 

 presentative of the order ; the so-called Macrotherium being now 

 known to be identical with the Ungulate genus Chalicotherium, while 

 Ancylotherium is also allied to the latter. In tropical Asia we find 

 the Pangolins or ManidcE ; and in Africa the OrycteropodidcE. South 

 America is, however, the headquarters of the order, which is there 

 represented at the present day by the Anteaters, the Sloths, and the 

 Armadillos, and in past epochs by the huge Ground-Sloths and the 

 Glyptodonts. The gigantic size of these fossil forms as compared 

 with their existing allies of the same area is paralleled by the in- 

 stance of the fossil Diprotodont Marsupials of Australia. 



It is evident that the Edentates are widely separated from all 

 other existing Eutherians ; and Professor W. K. Parker, in view of 

 the tendency to a variation in the number of cervical vertebrae and 

 other features, has suggested a separate origin from a Prototherian 

 stock. Professor Cope, however, looks upon the order as allied to 

 the Tillodonts, and the occurrence of enamel in the teeth of some 

 fossil forms may support this view. 



Family Orycteropodid^e. — The Ant-Bears (Orycteropus) of 

 Africa are characterised by the body being covered merely with a 

 few hairs ; and by the numerous teeth, which are of a remarkably 

 complex structure, owing to the presence of a number of vertical 

 pulp-canals. In the fore-limb the pollex is absent, but the hind- 

 limb has five digits. The femur has a third trochanter, and the 

 terminal digits are provided with moderate-sized claws, suitable for 

 digging the burrows in which these creatures dwell. At the present 

 day Orycteropus is mainly characteristic of the Ethiopian region, 

 although one of the two species ranges into Egypt. Till very re- 



