PETERSON : A REVISION OF THE ENTELODONTIDAD 77 
rently of considerably later age than the John Day formation in which Entelodonts 
have been discovered, judging from the fauna which has been published elsewhere 
(81, pp. 34-56). That some genera of the Mntelodontidx continued to the close of the 
lower Miocene is now well established ; indeed it would perhaps not be surprising to 
find them represented in the middle and possibly in the upper Miocene. Dinohyus, 
which was discovered in the upper part of the lower Miocene beds (lower Harrison 
beds), was in all probability followed in the Miocene in New Jersey, by Ammodon 
leidyanwm, which is without much doubt a later form. 
Derartep Description or Dinonyus Honianpr PErerson. 
Tue Superior DENTITION. 
(Plates LVII and LVIIL) 
The median pair of incisors are lost in the type, but the alveolus of the right 
side is complete, and indicates a proportionally small tooth. I* is present and is 
much worn on the apex and the internal face; the tooth ; 
has a crowded position, and its antero-posterior diameter 
is greater than the transverse. I* is the largest of the 
incisors and is about twice the size of 12; it has received 
much wear on the postero-lateral angle from contact with 
the inferior canine, and the apex is also much worn. ‘The 
antero-posterior diameter of this tooth is, as in its prede- 
cessor, the greatest. All the incisors are more crowded 
than in the Oligocene forms generally. It is also notice- 
able that the transverse groove immediately above the 
enamel band, which Professor Scott refers to. (87, p. 274), 
is very well developed in the type, and could not have 
been caused by the wear of the lower teeth. § 
Asin other forms of the family, the canine tooth is Fic. 29. ObliqueSide Views of 
very large, recurved, and has an enormous fang. In the paneer haceinige sy 
present specimen the apex of the tooth has received con- — poss., No. 2145.) 
siderable wear as has also the antero-internal face. There 
is a light cingulum on the posterior face, but externally the enamel is smooth. 
The first, second, and third superior premolars in Dinohyus are in general quite 
similar in shape to the corresponding teeth in Hntelodon magnum of Europe. They 
80. A premaxillary bone (No. 2145, Carn. Mus. Cat. Vert. Foss.) in the collection from the Agate Spring Fossil 
Quarries, (Quar. No. 1, Sect. 19), which is here referred to Dinohyus, has only two alveoli, the median incisor having 
dropped out and the alveolus closed. 
