XIII 



PHYLUM CIIORDATA 



525 



numerous chevron bones. In 3fanis, Oryderoptis and Myrmeco- 

 2)haga none of the neck-vertebroe are united. In the posterior 

 thoracic and the Uimbar regions of Myrmecophaga there are deve- 

 loped complex accessory articulations between the vertebrae. The 

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



derived from the caudal 

 region, a condition whicli 

 occurs also in Oryc- 

 teropus. 



In the Sloths none of 

 the cervical vertebrae are 



Pig. 1136.— Bones of right foot of 

 Kangaroo ( Macro^ms bennetii.) 

 a. astragalus ; c. calcaneum ; cb. 

 cuboid ; «3. ento-cuneiforiu ; 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 (Cholcepus hoffmanni) 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 



JF 



Fu;. 1135.— Bones of leg and foot of Fhalanger. agt. 



astragalus; ailc. calcaneum; cub. cubl^id ; eft. cun. 

 ecto-cuneiform ; ent. cun. eiito-cuneiform ; ff>. fibula ; 

 Mies. cun. nieso-cuneiform ; nar. navicular ; tih. tibia. 

 (After Owen.) 



VOL. II 



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