1893.] The Ancylopoda, Chalicotherium and Artionyz. 127 
“buno-selenodont.” The feet are in the border region between - 
the unguiculates and ungulates. This genus also occupies an 
isolated position; although placed by Cope in the family 
Meniscotheriide among the Condylarthra it is not even 
remotely related to any of the contemporary ungulates. Its 
molar evolution was precocious in both jaws, far more so than 
in Phenacodus. I was led to the idea that this might possibly 
be the long sought ancestor of Chalicotherium by the struct- 
ure of the molar teeth. In 1886 Wortman regarded Menisco- 
therium as an ancestor of the Hyracoidea. Later Schlosser 
recognized the striking likeness of its molars to those of Chal- 
icotherium, and considered it with Macrauchenia as a repre- 
sentative of Perissodactyla which had retained a primitive 
foot structure. 
The comparison of the entire dentition of Meniscotherium 
and Chalicotherium led me in 1891 to the discovery of many 
very significant details of resemblance. In both, the anterior 
portion (or cutting teeth) of the dental series is reduced and — 
the posterior or cheek teeth are enlarged. In both, the true 
molars have identically the same pattern in detail in both 
jaws, including the absence of the third lobe upon the last 
lower molar, which separates Meniscotherium from all early 
Condylarthra and Perissodactyla. I was especially struck 
also by the presence of a short posterior crest formed of the 
hypocone and hypoconule in the upper molars, and by the 
reduplication of the antero-internal tubercle (metaconid) in 
the lower molars. At the tinie only the upper tarsals of Men- 
iscotherium were known; these possess the unguiculate char- 
acters which are exhibited in Phenacodus and all early ungu- 
lates but are distinguished by a fibular facet upon the calca- 
neum. It appeared to me altogether probable that the Wahsatch 
form was related to the ancestors of Chalicotherium, and that 
the question would be decided by the discovery of its feet. 
This discovery was reported sooner than was expected in 
Marsh’s recent paper upon M. (Hyracops) sociale in which the 
fore and hind feet are fully figured. — 
‘The feet of Meniscotherium present only one feature which 
definitely points to those of Chalicotherium, namely, they are 
