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1884.] The Condylarthra. 791 
tured the generalization that the primitive types of the Ungulata 
would be discovered to be characterized by the possession of five- 
toed plantigrade feet, and tubercular teeth. No Perissodactyle or 
rtiodactyle mammal was known at that time to possess such feet, 
nor was any Perissodactyle known to possess tubercular teeth. 
Shortly after advancing the above hypothesis, I discovered the 
foot structure of Coryphodon, which is five-toed and plantigrade, 
but the teeth are not of the tubercular type. For this and allied 
genera I defined a new order, the Amblypoda. 
In 1873' I described, from teeth alone, a genus under the name 
of Phenacodus, and although a good many specimens of the 
dentition came into my possession since that date, I was long 
unable to assign the genus its true position in the mammalian 
class. The teeth resemble those of suilline ungulates, but I. had 
never had sufficient evidence to permit its reference to that 
group. Ailied genera, subsequently discovered by me, were 
stated to have a hog-like dentition, but their position could not 
be determined until the structure of the feet should be ascer- 
tained? : 
In his explorations in the Wasatch Eocene of Wyoming, in 
1880, Mr. J. L. Wortman was fortunate enough to discover nearly 
entire skeletons of Phenacodus primevus and P. vortmani, which 
Present all the characters essential to a full determination ot the 
Place of Phenacodus in the system. The result is, that this 
Senus must be placed in a special group of an order which in- 
application. Thus Kowalevsky remarks (Monographie der Gattung Anthracother- 
ium, Palæontographica, XXII, p. 1452): “So we can assume a tetradactyle foot as 
2 , but I communicated the substance of the generalization in 
Westion to the Philadelphia Academy the day it was read, Nov. 18th, 1873» which 
Was Published in the Proceedings of the Society, Jan. 13, 1874 (see p. ii). 
! Palæontological Bulletin No. 17, Oct., 1873, p- 3; also Report G. M. Wheeler 
- S. Engineers Expl. W. 100 mer., IV, p. 174, 1877. In the figure of the superior 
teeth in this work, the last molar is misplaced. 
eds. Amer. Philosoph. Society, 1881, p. 495. 
2 
