186 COPE. [Vor. III. 
series of tarsals in the extinct Amblypoda (Fig. 8). Any one 
who has examined this part of Cory- 
phodon will see that a little addi- 
tional mobility at this point would 
soon resemble the second tarsal joint 
of the Hippopotami, etc. In the 
case of animals which progress on 
hard ground, no such cross-strain 
would be experienced, and the effect 
would be to consolidate by flattening the 
fixed articulation. And this is what has 
occurred in the Perissodactyla, beginning 
with the oldest known forms. 
e. The Tarsal Articulations of the Eden-. 
tata. The peculiarities of the tarsal artic- 
ulations in the Edentata have reference 
to the lateral direction of the sole of the 
posterior foot in the families Megathe- 
riide, (Megalonyx,) Bradypodidz, and 
Myrmecophagide. This semisupination 
is accomplished in two ways: Ist, by an 
Figure 25.— A, Bradypus tridactylus 1, posterior foot, from behind, nat. size: 
from Cuvier. B, Cholepus didactylus L., tarsus and end of leg, from behind, natural 
size: from Cuvier, Oss. Foss. @, Astragalus with peg and socket articulation of 
fibula. 
