- THE 
AMERICAN NATURALIST 
VoL. XXXI. June, 1897. 366 
TOXODONTIA. 
By E. D. Copr. 
In this order of Ungulates the carpus is partly diplarthrous, 
while the tarsus is taxeopodous. The carpus is quite like that 
of the Amblypoda, the scaphoid bone not extending external 
to the trapezoides, while the lunar has a well-marked articula- 
tion with the unciform. The tarsus, on the other hand, is 
like that of the Taxeopoda in general, but adheres strictly to 
the Ungulate type in the truncate and non-moveable articula- 
tion of the astragalus with the succeeding element, the navi- 
cular. The ungues vary from broadly to narrowly ungulate ; 
as in Toxodon they resemble those of a rhinoceros, and in Ty- 
potherium those of some of the subungulate Glires, as the 
Capybara. The known members of the order are plantigrade, 
or nearly so. In all of them the fibula articulates with the 
calcaneum. In some of them there is no clavicle, while in 
others it is present. The dentition is lophodont, becoming 
ptychodont in some of the later forms; quadri- and tritu- 
bereular forms being unknown. In details the families and 
genera differ much among themselves. I therefore consider 
the further characters under the respective heads. I adopt 
the system of Ameghino, which seems to express their affini- 
ties very closely. 
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