132 The American Naturalist. [February, 
As Chalicotherium may be broadly termed an unguiculate 
perissodactyl,so Artionyx may be called an unguiculate artio- 
dactyl. This, in fact, sums up the main difference between 
these types when we add that the terminal phalanges in the 
former are cleft, and in the latter are uncleft. 
If this foot of Artionyx had the metatarsals cut off half way 
down, no one would hesitate to call it truly artiodactyl. The 
tibia, fibula, astragalus and calcaneum, the navicular with its 
posterior hook for the great-flexor tendon, the conjoined 
ecto- and mesocuneiforms, the nearly even pairs of toes on 
either side of the middle line—all these structures bear a 
marked artiodactyl stamp. The entocuneiform is missing, 
but there is no doubt that it supported a first digit, of which 
the proximal phalanx is fortunately preserved. 
The distal ends of the metatarsals and the phalanges exhibit 
the same sudden transition to an unguiculate type which we 
observe: in Chalicotherium, in fact they bear a very marked 
resemblance to the corresponding parts in the feet of the 
carnivora, until we come to the terminal phalanges, which are 
short, deep and laterally compressed, but not hooked or retrac- 
tile. As observed above, they are not cleft. 
The foot differs as widely from that of Chalicotherium as 
that of the pig does from that of the tapir. It is somewhat 
hazardous to make a deduction from the foot alone, but wè 
have ventured to divide the Ancylopoda into two subdivisions. 
TEREE. SUB-ORDERS. 
Aneylopoda. Ungulate, with A. Perissonychia (odd clawed), 
unguiculate terminal phalanges. with perissodactyl tarsus and 
mesaxial reduction. Ungues cl 
B. Artionychia (even clawed), 
with artiodactyl tarsus and parax 
jal reduction. Ungues uncleft. 
Subsequent discoveries may show that these are merely twO 
families—the Chalicotheride and Artionychide. This discov- 
ery rather strengthens the idea of the relationship of Menis- 
cotherium to the Ancylopoda—for we observe in Artiony* the 
fibulo-calcaneal facet of the older genus, also the depression 
upon the inner side of the astragalus. 
