XIII 



PHYLUM CHORDATA 



493 



numerous chevron bones. In Manis, Orycteropus and Myrmeco- 

 phaga none of the neck vertebrae are united. In the posterior 

 thoracic and the lumbar regions of Myrmecophaga there are deve- 

 loped complex accessory articulations between the vertebrae. The 

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



derived from the caudal 

 region, a condition which 

 occurs also in Oryc- 

 teropus. 



In the Sloths none of 

 the cervical vertebrae are 



FIG. 1067. Bones of right foot of 

 Kangaroo (Macropus bennetii.) 

 a. astragalus ; c. calcaneum ; cb. 

 cuboid ; e3. eiito-cuneiform ; n. 

 navicular. (After Flower.) 



ankylosed together; but 

 in the three-toed Sloths 

 there is an important 

 divergence from ordinary 

 Mammals in the number 

 of vertebrae in the cervi- 

 cal region, being nine instead of seven ; while in one species of two- 

 toed Sloth (Cholcepus Jioffmanni) 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 



FIG. 10(56. Bones of leg and foot of Phalanger. ast. 

 astragalus ; calc. calcaneum ; " cub. cviboid ; ect. cun. 

 ecto-cuneiform ; cnt.cun. ento-cuneiform ; fb. fibula ; 

 mes. cun. meso-cuneiform ; nac. navicular ; fife, tibia. 

 (After Owen.) 



