348 Bulletin American Museum of Natural History. (Vol. XXXIV, 
to that of Phenacodus and unlike that. of any other Wasatch form. The 
arrangement of the cusps also corresponds with Phenacodus in a general way, 
but the tooth differs in the enlargement of the protoconule and in the 
more swollen and rounded appearance of all the cusps. ‘The protocone is 
the largest of the cusps and the metacone and hypocone are reduced and the 
metaconule and mesostyle are absent. The absence or extreme reduction 
of mesostyle and metaconule is, however, not rare in the m? of Phenacodus. 
I do not have much hesitancy in placing this type as a somewhat abnormal 
tooth of Phenacodus. In size it agrees most closely with the smaller variety 
of P. prumevus. Measurements are: tr. = 11.2 mm., antero-post. = 10.2 
mm. 
E. (?)superstes 
(Gray Bull beds, Bighorn basin, 
Wyo.) 
E. osbornianus 
(Type, Gray Bull beds, Bighorn 
basin, Wyo.) 
E. ralstonensis 
(Paratype, Clark Fork beds, 
Clark Fork basin, Wyo.) 
Fig. 11. Upper teeth of species of Ectocion. 
Ectocion Cope, 1882.' 
Type. Oligotomus osbornianus Cope, 1882, from the Wasatch of the 
Bighorn basin, Wyo. 3 7 
Cope based this genus upon a single poorly preserved ‘specimen in his 
collection from the Wasatch of the Bighorn basin. In his Tertiary Verte- 
brata he placed the genus in the Chalicotheriidse, but suspected its affinities 
with the Condylarthra to the extent of pointing out its difference from Tetrac- 
lenodon and Phenacodus. The forward position of the metaconule, similar 
to that in Kohippus, seems to have been the character which led Cope to 
consider Ectocion a Perissodactyl of a primitive sort, with the metaconule 
1 Amer. Nat., p. 522. 
