218 MEMOIRS OF THE CARNEGIE MUSEUM 
I. acutidens. This specimen has no convexities on the top of the skull above the 
orbits like those in I. montanus. ‘The post-orbital constriction is slightly more 
noticeable than in the latter species. The post-glenoid process is small and _ short. 
The mastoid process of the squamosal is quite long antero-posteriorly but does not 
extend down so far and curve as much as it does in I. montanus. 
The Mandible. —The lower jaw is fairly deep and heavy. All the teeth are pre- 
served. ‘There are three incisors on each side, of nearly equal size. They are semi- 
procumbent and their arrangement is nearly fore-and-aft parallel to the long axis 
of the jaw. 
The canine is quite long, straight, and slender, and, like the incisors, is semi- 
procumbent, being directed more forward than upward. It is close to the third 
incisor; ¢here being no space between them. 
P; is small, apparently one-rooted, is directed forward, and is low crowned. 
Pz is much larger, more erect, yet directed slightly forward. It has a hint of a 
heel or small basal cusp. 
P# is nearly erect, has a small posterior cusp and a rudimentary anterior one. 
P+ has a distinct anterior cusp and a well developed basal heel. 
The molars are about equal in size but are so worn that the relative proportions 
of their various cusps cannot be determined with certainty. 
The horizontal ramus of the mandible is moderately deep and heavy. It 
deepens gradually from the incisors backward to the last molar. The angle is 
injured. ‘The masseteric fossa is deep and the anterior border of the edge of the 
ascending ramus is a narrow ridge. 
Ictops tenuis sp. nov. 
Carnegie Museum Collection, No. 1021. 
An adult, but not old. 
Found in Titanotherium Beds southeast of McCarty’s Mountain near the same 
level as the type of Ictops intermedius, and somewhat higher than that of . montanus. 
Of this specimen we have the anterior portion of the skull with the snout complete, 
the left ramus of the mandible lacking the top of the coronoid process, a radius, parts 
of the ulna and tibia, fragments of ribs, and other bones. 
PrincrpaAL CHARACTERS.— Thisis larger than either of the specimens previously described. 
The most noticeable differences besides the greater size are the greater width of the palate 
between the teeth and the much greater width at the post-orbital constriction. The teeth are 
wider in proportion to the length than i I. montanus. The palate, though 40 per cent. 
wider at M*, is nearly the same width at P+as that of I. montanus. The muzzle is 
