xtli 



PHYLUM CHORDATA 



50$ 



both by their bodies and by their neural arches. In the lumbar 

 region the metapophyses are greatly prolonged longer than the 

 transverse processes and support the bony carapace. A re- 

 markable peculiarity of the spinal column in the Armadillos is 

 the fusion of a number of the anterior caudal vertebrae with the 

 true sacrals to form the long sacrum, containing as many as ten 

 vertebras altogether (Fig. 1158). The caudal region is of moderate 

 length ; there are numerous chevron bones. In Manis, Orycteropus, 

 and Myrmecopkaga none of the neck-vertebrae are united. In the 

 posterior-thoracic and the lumbar regions of Myrmecophaga there 

 are developed complex accessory articulations between the vertebras : 

 the sacrum contains, in addition to the true sacral vertebrae, a 

 number derived from the caudal region, a condition which occurs 

 also in Orycteropus. 



In the Sloths none of the cervical vertebrae are ankylosed together ; 



max 



Icr 



FIG. 1146. Skull ofWombat (Phascolomys icombat) (lateral view). Letters as in Figs. 1144 

 and 1145. In addition, ext. aud. opening of bony auditory meatus ; cond. condyle of mandible 



but in the three-toed Sloths there is an important divergence from 

 ordinary Mammals in the number of vertebrae in the cervical region, 

 there being nine or ten instead of seven ; while in one species of 

 two-toed Sloth (Cholospus hqffmanni) there are only six. The 

 neural spines of all the vertebrae are very short. A number of the 

 anterior caudal vertebrae are united firmly, though not quite fused, 

 with one another and with the true sacrals. 



In the Armadillos the sternal ribs, which are sub-bifid at their 

 sternal ends, are ossified, and articulate with the sternum by means 

 of well-developed synovial articulations. In the American Ant- 

 eaters there are similar synovial joints, and the sternal ends of the 

 sternal ribs are completely bifid. In the Sloths the sternum is 

 long and narrow, and there are no synovial joints. In front the 

 sternal ribs are ossified and completely united with the vertebral 

 ribs, but behind they are separated from the latter by intermediate 

 ribs which are less perfectly ossified. 



VOL. II I I 



