E. L. Troxell — American Bothriodonts. 329 



' ' The three conical buttresses on the outer border of this tooth, 

 all strongly developed, will serve to distinguish it from the cor- 

 responding molar of Hyopotamus, which in several respects it 

 resembles. In that genus, the main cusps are much more ele- 

 vated. Heptacodon, perhaps an allied form, has a similar but- 

 tress at the anterior angle, but none at the posterior. An upper 

 incisor found with the present tooth, and doubtless pertaining to 

 the same individual, has a very short, compressed crown, with a 

 strong inner basal ridge, making the inner face deeply concave. ' ' 



The low cusps, absence of cingula excepting a weak one 

 anteriorly, the prominence of the three styles, and 

 especially the para- and mesostyles, the shallowness of the 

 transverse valley which ends between the para- and 

 metacone, the distinct ridge from the cusp of the meso- 

 style forming a Y with ridges from the para- and meta- 



FiG. 2.—Octacodon valens Marsh. Holotype. Cat. No. 11860, Y. P. M. 

 Crown view of M^ After Marsh. Nat. size. 



cones, the short antero-posterior and the great transverse 

 diameter anterior, and the general smoothness, are all 

 features which separate the species from those of any 

 other genus. 



Octacodon gihbiceps (Marsh). 



(Fig. 3.) 



Holotype, Cat. No. 10194, Y. P. M. Upper Oligocene (Protoceras beds), 

 Hermosa, South Dakota. 



The original description, under Heptacodon, is in part 

 as follows :^^ ' 



''The facial portion of this skull is strongly rounded above, 

 especially in the frontal region, and this has suggested the speci- 

 fic name. The orbits are large, and not closed behind, although 

 limited posteriorly by strong processes above and below. There 

 is no antorbital depression, and the lachrymal foramen is inside 



'°0. C. Marsh, This Journal (3), 48, 175-176, 1894. 



