1881.] 403 
[Cope. 
specialization of that order. The posterior feet were more truly planti- 
grade. for the extremity of the calcaneum reached the ground, while the 
instep was elevated above it, being supported, no doubt, by a more or less 
elastic pad. This arched or angulate plantigrade type of foot, has a remote 
parallel in that of man. It is quite unique among ungulate Mammaiia. 
What difficulties the other parts of the skeleton may present, I do not yet 
know, but I perceive nothing in the dentition which forbids the reference 
of Toxodon to the Proboscidia. The dentition is scarcely more ditferent 
from that of Mastodon or Dinotherium, than that of Bos is from Dicotyles 
or Hippopotamus. The former genera may be the extremities of a series 
whose intermediate members are as yet undiscovered. In the latter case, 
the intermediate forms are mostly known. 
Printep May 177TH, 1881. 
