DOUGLASS: THE TERTIARY OF MONTANA 213 
In his ‘Tertiary Vertebrata, p. 265, Cope, after the discovery of a skull and mandi- 
ble of Ictops (Palexictops) bicuspis and a fragment of a mandible of LI. didelphoides, 
gave the following generic characters. Dental formula I$, C}, Pm#¢, M3. “Third 
superior premolar tooth with two external and an internal cusp; fourth premolar 
like the true molar, with two external tubercles, an internal tubercle, and a pos- 
terior cingulum. Fourth inferior premolar with an internal and a well developed 
anterior tubercle ; the anterior tubercle of the true molars median in position, and 
much smaller than the internal tubercle. Heels of molars with elevated cusps. 
Orbits not closed posteriorly. Coronoid process of mandible well developed. 
Inferior margin of mandible not inflected.” 
With regard to the systematic position Cope says, ‘ Ictops agrees very closely with 
Didelphys. he fourth superior premolar has an internal cusp, which is wanting in 
Didelphys, and the inferior border of the mandible is not inflected. There are also 
but three superior incisors on each side. Under these circumstances I prefer to refer 
this genus to the Bunotheria rather than to the Marswpalia, but whether its proper 
place is in the Creodont or Insectivorous subdivisions I cannot yet determine.” 
On page 800 of the Tertiary Vertebrata Cope says that Leptictis, Ictops, and Meso- 
dectes belong to a distinct division from Peratheriwm and Domina and that this 
division is perhaps of ordinal value, but it remains uncertain on account of the 
incompleteness of the specimens. 
Species oF Icrops. 
Ictops didelphoides Cope. 
Bull. U. 8. Geol. Surv. Ter., VI., p. 192. Figured in Cope’s Tertiary Vertebrata, 
Jl, ROR Gp, 1a, 8). 
It is represented by a fragment of a lower jaw with three teeth. This may 
not be Jctops at all, and if so it is of very little use for our purpose. 
Ictops acutidens Douglass. 
This species was found in the Titanotherium Beds of Pipestone Springs, Montana, 
and described by Douglass.' It is represented by an upper jaw with the five posterior 
teeth, the lower jaws with the molar teeth and one premolar — the anterior Portions 
of both rami absent — a lumbar vertebra, a femur, part of a tibia, an astragalus, and 
acalcaneum. It is a rather young individual, but probably nearly full grown. In 
my paper I gave a general description, but did not give a clear diagnosis of the dis- 
tinguishing specific characters as they were not then known, the only species really 
1 Fossil Mammalia of the White River Beds of Montana, Trans. Am. Phil. Soc., N.S., Vol. XX., p. 245. Reprint 
p: 9. 
