| 
| 
| 
58 MEMOIRS OF THE CARNEGIE MUSEUM 
Locality: Bad-lands of South Dakota. 
Locality of Type: Collection of Yale Museum, No. 12030. 
The tooth figured in 1893 by Professor Marsh (68, Pl. IX, fig. 4), and referred 
to the genus Ammodon, though inadequate as a type, fortunately shows characters 
which at once separate it from Ammodon leidyanwm, not only specifically, but also 
generically (see fig. 13). In Marsh’s original description in 1874 (59, p. 534), he 
gives the principal characters of My of his proposed species “‘ Hlotheriwm”’ bathrodon, 
which constitute the chief differences between that tooth of the latter species and 
the genus Ammodon. Marsh says: “This molar differs essentially from the same 
Fig. 13. Last Lower Molar of P. bathrodon Marsh. } nat. size. (After Marsh.) 
tooth in the other known species of this genus [Hlotheriwm], especially in having 
the anterior pair of tubercles much larger than the posterior pair, and elevated high 
above them.” * On comparing Marsh’s figures reproduced in this connection (fig. 
13) it is at once seen that the tubercles are more distinctly separated by narrow 
longitudinal valleys, and that the cross-valley between the anterior and posterior 
tubercles is open and very broad, which is due to the small development of the pos- 
terior tubercles; a character common to the older American types of the family 
Entelodontide. In Ammodon and Dinohyus the development of the posterior tuber- 
cles (ento- and hypoconids) is relatively greater and the cross-valley is very much 
reduced in the antero-posterior direction. The distinct development of the fifth 
cone (hypoconid) in Ammodon leidyanuwm seems to have progressed in the same gen- 
eral ratio as that of the posterior tubercles. 
In the Yale Museum is a specimen of an Entelodont, which was collected in 
1890 by Mr. J. Brown and bears the catalogue number 10008. This specimen is a 
skull of a large individual apparently from the Protoceras sandstones of the Oligo- 
cene. The front and back of this skull is broken off so that its length cannot be 
ascertained. The size of the molars corresponds quite well with that of the tooth 
described by Marsh as the type of Pelonax bathrodon, and, from the fact that it was 
'8 This elevated position of the anterior portion of the crown seems to be greater than in Pelonax potens. 
