1374 THE EDENTATES 



low degree of organization, although many of them are specialized for particular 

 modes of life. In general their brains are relatively small, with the hemispheres, 

 or anterior portion, devoid of convolutions, and not extending backward to overlap 

 and conceal the hinder portion or cerebellum. In some cases, however, the hemi- 

 spheres of the brain are distinctly convoluted. Very frequently the shoulder blade, 

 or scapula, is characterized by the great development of the anterior portion of its 

 lower extremity; this so-called coracoid portion (of which we shall have to speak 

 more fully when we come to the Egg-laying Mammals), being sometimes, as shown 

 in our figure of the skeleton of the sloth, marked off from the remainder of the bone 

 by a perforation, and suturally united with it. Certain members of the order, such 

 as the armadillos and their extinct allies, are peculiar among Mammals in possessing 

 a bony cuirass in the skin; while the pangolins are equally remarkable for the coat 

 of overlapping horny scales with which the entire body is invested. 



From the absence of enamel in their teeth, and the presence of rudimental milk- 

 teeth in some of their representatives, it is probable that the Edentates should be 

 regarded as somewhat degenerate types, descended from ancestors provided with a 

 double set of enamel-coated teeth. There are, however, no indications of any close 

 relationship between the Edentates and any other of the Mammalian orders, and it 

 is accordingly pretty evident that they are descended from extinct primitive Mam- 

 mals quite independently of all other members of the class. 



As already mentioned, the sloths, ant-eaters, and armadillos, are 

 entirely confined to the New World; and since it is these alone which 

 form the typical Edentates, the order is essentially an American one. Indeed, there 

 is a considerable degree of doubt whether the Old-World pangolins and aard-varks, 

 which form its only other representatives, are rightly included within the order; 

 their organization being very different from that of the typical forms. Be this as it 

 may, the typical Edentates appear to have been always confined to the New World, 

 in the southern half of which they attained their greatest development; for while 

 fossil forms are abundant in America, they are unknown elsewhere.* Some of these 

 extinct types are of the greatest importance to the zoologist, since they serve to 

 connect most intimately such widely different forms as the arboreal sloths and the 

 terrestrial armadillos. 



Although varying greatly in their mode of life, the whole of the 

 Edentates both living and extinct are either arboreal or terres- 

 trial, none of them being modified either for flight in the air or for swimming in the 

 water. While the purely arboreal sloths are entirely vegetable feeders, all the other 

 members of the order, of which a few are likewise more or less arboreal in their 

 habits, subsist on flesh or insects. Moreover, several of these carnivorous forms are 

 burrowing animals; and it is remarkable that the members of three distinct groups, 

 namely, the ant-eaters, the pangolins, and the aard-varks, subsist mainly, or exclu- 

 sively, on white ants or termites; the only other purely ant-eating members of the 

 class belonging respectively to the Pouched Mammals and the Egg-laying Mam- 

 mals. It is further noteworthy that while among the ant-eating Edentates the true 



* Certain remains from the Tertiary rocks of France have been considered to belong to armadillos, but 

 this determination is exceedingly doubtful. 



