HISTORY OF THE EDENTATA 599 



collected is so fragmentary that family distinctions have little 

 meaning. After all, there was no very wide range of variation 

 among the contemporary members of the three families, and 

 the differences were principally in size, in the form and number 

 of the teeth, the shape of the skull and the number of digits ; 

 in essentials they were all much alike. 



The genus ^Megatherium (Fig. 122, p. 220) included the 

 largest and most massive members of the suborder, ■\M. america- 

 num being as large as an elephant, but very differently propor- 

 tioned, as it was much longer and lower in stature, owing to the 

 shortness of the extraordinarily heavy limbs ; some of the 

 skeletons measure 20 feet or more in length. The teeth, which 

 were | in number, formed an uninterrupted series on each side ; 

 all had the same quadrate form and by abrasion were worn 

 into two transverse ridges, formed by the meeting of the harder 

 dentine with the thick coating of cement. The result was a 

 form of tooth which much resembled the lower molars of a 

 tapir, but it was not a tooth-pattern in any proper sense of 

 the word, being due entirely to the mode of wear. 



The skull was very small in proportion to the huge body 

 and was low and narrow in shape ; the cranium had a broad, 

 flat roof, without sagittal crest ; the orbit was completely 

 encircled in bone, and the descending process of the zygomatic 

 arch beneath the eye was very long and conspicuous. The 

 nasals were short, and the slender, toothless premaxillaries 

 projected far in front of them, which makes the presence of 

 some sort of a proboscis likely. The lower jaw had a long, nar- 

 row, spout-like symphysis, which was abruptly rounded at the 

 free end, not pointed ; below the teeth, the lower margin of 

 the jaw was very strongly convex, descending in a great flange. 

 The neck was short, the body very long and enormously heavy, 

 as was also the tail. The immense shoulder-blade had a very 

 long acromion, which curved forward and inward, fusing with 

 the coracoid and forming a bony loop or bridge. The hip- 

 bones had the anterior element (ilium) enormously expanded 



