184 Darwin, and after Darwin. 
them. This, of course, would give a weak foot, suited 
to slow progression over marshy ground—which, as 
= wae 
(After Cope.) 
Fic. 80.—Fossil skeleton of Phenacodus primevus. 
we have seen, was no doubt the origin of the mam- 
malian plantigrade foot. Here, for instance, to all in- 
tents and purposes, is a similar type of foot, which 
