XIII 



PHYLUM CHORDATA 



525 



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. 1136. Bones of right foot of 

 Kangaroo (Macropus bennetii.) 

 a. astragalus ; c. calcaneum ; cb. 

 cuboid ; e3. ento-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, there being nine or ten instead of seven; while in one 

 species of two-toed Sloth (Ckolcepus 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 



FK;. 1135. Bones of leg and foot of Phalanger. ast. 

 astragalus ; calc. calcaneum ; cub. cuboid ; ect. cun. 

 ccto-cuneiform ; ent. cun. ento-cuneiform ; fb. fibula ; 

 mes. cun. meso-cuneiform ; nav. navicular : tib. tibia. 

 (After Owen.) 



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