O. C. Marsh—American Surassic Mammals. 339 
Docopon. 
Another genus (Docodon) of this family may be distin- 
guished from Diplocynodon by having, in the lower jaw behind 
the canine, eleven teeth instead of twelve. The canine has 
two fangs, as in the latter genus, and the molar teeth corres- 
pond closely in form. The symphysis is very long, and the 
mylohyoid groove extends forward to its upper border. The 
type specimen of this genus is shown in Plate X, figure 2. 
In Docodon, the dental foramen is further back than in 
Diplocynodon, and the mylohyoid groove, leading out of it, 
is deep and straight as far as the last premolar. 
ENNEODON. 
A third genus, Hnneodon, described below, is represented by 
two specimens, one of which is shown on Plate X, figure 4. 
The lower jaw is comparatively short and robust, and contained 
only nine post-canine teeth, all of the same type. 
Enneodon crassus, gen. et sp. nov. 
The canine in Hnneodon is large, and, as in the other genera 
of this family, is inserted by two well-separated fangs. Seen 
from the outside, its crown resembles that of a true molar, but 
the anterior lobe is wanting. The second premolar is larger 
than the first, not smaller, as in the type of Diplocynodon. 
The premolars, although of the same general form as the 
molars, have the surface of the crown more grooved, or striate. 
Enneodon affinis, sp. nov. 
A second specimen of this genus agrees with that last de- 
scribed in the main features of its dentition, but the lower jaw 
is less robust. The canine is also more slender, and there is a 
small diastema behind it. The first three premolars increase 
in size backward, but are all of similar form. The angle of 
the jaw is considerably below the lower margin of the ramus. 
The principal dimensions of this specimen are as follows: 
Space occupied by nine premolar and molar teeth ___..... 16°™™ 
Wepth otjaw: below: first: premolar 20522) .ch2 0 2 
Wepinot jaw, below, first molar, 62220052 yl. 3°25 
Persht of first premolar-above jaw ..-.-2.-..2.--....1.- 1°5 
Heishtiot second molarjaboveijaw ..-...--2.5.......--- 2° 
Antero-posterior diameter of second molar_._.._._.-..--- 2° 
The fossils on which the two species of Hnneodon are based 
were found in the Atlantosaurus beds of the Upper Jurassic, in 
Wyoming. 
