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 MyrmecopTbaga there are deve- 

 loped complex accessory articulations between the vertebra?. 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 



ent.cun 

 me&.cun 



FIG. 1067. Bones of right foot of 

 Kangaroo (Macroi)iis bennetii.) 

 a. astragalus ; c. calcaneum ; <:>>. 

 cuboid ; (A 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, being nine instead of seven ; while in one species of two- 

 toed Sloth (Clwlcepm ho/manni) 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 

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



FIG. 1066. Bones of leg and foot of Phalanger. ast. 

 astragalus; ca/c. calcaneum ; cul>. cxiboid ; ect. cun. 

 ecto-cuneiform ; ent.cun. ento-cuneiform ; j'>. fibula ; 

 Jin.*. c*'<>. meso-cuneiform ; n<:<.<-. navicular; tib. tibia. 

 (After Owen.) 



