ARMADILLOS. 325 



In the Glyptodon the vascular osseous texture(l) occupies a 

 larger proportion of the centre of the tooth than in the small Arma- 

 dillos : it is harder than the dentine or cement, and rises upon the 

 grinding surface (2) in the form of a ridge extending along the 

 middle of the long axis of that surface, and in three shorter ridges 

 at right angles to the preceding, at the middle of each of the three 

 rhomboidal divisions of the tooth. The medullary canals are sur- 

 rounded by fine compact concentric strata, but are wider than in 

 true bone, and the calcigerous cells are fewer and less conspicuous : 

 the canals bend towards the dentine, but without any regular or 

 parallel arrangement. The calcigerous tubes(3) assume their parallel 

 and regular course sooner than in the Armadillos : they have the 

 same relative diameter, arrangement, and terminal ramification. The 

 outer coat of cement (4), though not exceeding n,th of a line in thick- 

 ness, is relatively thicker than in the Armadillos ; a large proportion 

 of the terminal branches of the calcigerous tubes is continued into 

 it, and these branches anastomose with the plexiform tubes which 

 surround the calcigerous cells. These cells, which generally present 

 an oblong form, are about a^geth of an inch in their long diameter. 



Although the teeth of the largest of the extinct loricated Bruta, 

 present so much more complicated a form than do those of the 

 small existing species, their intimate texture and composition are 

 essentially the same, and very distinct from what has been described 

 in the Orycteropus and will subsequently be shown to charac- 

 terize the dentition of the family of the Sloths. Nevertheless, 

 the modification in regard to the proportions of the constituent 

 textures of the molars of the Glyptodon, which produce the in- 

 equality in the grinding surface of the crown, coincide with the 

 more complicated form of that surface, in adapting the tooth for 

 a more strictly vegetable diet than is indicated by the more simple 

 molars of the existing Armadillos. It is interesting to find that 

 the herbivorous character of the dentition of the Glyptodon was 

 associated with a descending process of the malar bone(5), which, 

 in the Sloths, affords the masseter muscle, a more extensive and 



(1) PI. 86, fig. 3, a. (2) lb. fig. 2. (3) lb. fig. 3. b, b. (4) lb. fig. 3, c. 



(5) Geol. Trans. 2ncl series, vol. vi. p. 86. 



