236 O. C. Marsh—New Orders of Jurassic Mammals. 
composed of a main external cone, with a small elevated lobe 
in front, and a lower one behind. This is repeated on a re- 
duced scale on the inner side, except that the posterior small 
cusp is rudimentary or wanting. The antero-posterior faces of 
the crown are deeply excavated, and grooved. ‘There is no 
cingulum. 
The jaw is elongate, and gently curved below. The coro- 
noid process is large and elevated. The condyle is placed very 
low, nearly on a line with the teeth. The angle of the jaw 
is produced into a distinct process, the lower margin of which 
bends outward, although the process asa whole has a slight 
es 
eel. The outer face and the sides of the upper molars are 
deeply sculptured with irregular grooves. 
Stylacodon validus, sp. nov. 
Since the discovery of the type of this genus,* two other 
allied specimens have been brought to light, one of which, also 
a lower jaw, proves to be new. This indicates a species much 
larger than the one first described, but apparently belonging to 
the same genus. e molar teeth in this jaw are inserted 
by a single fang. The anterior premolars preserved have each 
jaw. They have one main external cone and three inner cusps, 
thus agreeing in general form with the molars of Dryolestes. 
The mylohyoid groove is distinct, and continues forward nearly 
to the symphysis. 
Some of the dimensions of this specimen are as follows : 
Space occupied by eight anterior molar teeth,... 10°0"" 
Depth of jaw below first lower premolar, -- ---- - 3°0 
Depth of jaw below fourth premolar, ---.---- -- BS 
Height of crown of fourth premolar, ---- .--- - aeeVE 
Tinodon ferox, sp. nov. 
*This Journal, xviii, p. 60, July, 1879. 
