50 MEMOIRS OF THE CARNEGIE MUSEUM 
with that of A. crasswm, but is smaller, “the malar process is quite slender and 
tapering below [and] extending downward. . . . The dentition agrees in the main 
with that of H. [A.] crassum, the last lower molar in each having four cones only, and 
no heel.” The malar arch and the dependent angle of the lower jaw, which Pro- 
fessor Marsh states, “ will distinguish it from A. mortoni,” are found to be present and 
more or less developed in all the specimens of this family found in America with 
these parts preserved. 
In my notes on the type of Archxotheriwm clavum taken in the Yale Museum I 
find the following statements, which tend to show that Marsh’s species should at 
least be given a subspecific rank : 
“The general contour of the skull is much the same as that of A. crassum, the 
occiput is not overhanging, the anterior border of the orbit is opposite the middle 
portion of M®, the antorbital foramen is large and placed over P*. Premaxillaries 
produced forward giving plenty of room for the incisors, which are separated by 
Fie. 7. Skull of Archxotherium clavum Marsh. About + nat. size. (After Marsh. ) 
diastemata except I+ and I. The latter are, however, well separated at the apices. 
The orbit is placed slightly higher than in A. crasswn. The dependent broad pro- 
cess of the jugal is not large, and, as Marsh stated, points directly downward and 
also slightly outward. The zygomatic process perhaps did not reach to the anterior 
border of the glenoid cavity. The condyles are well separated superiorly and inferi- 
orly and the paroccipital process is rather short and truncated. ‘The foramen mag- 
num is large and subtriangular in outline. The chin has a considerable slope and 
is quite convex from side to side. The anterior knob-like protuberances are not 
large and are placed well back asin some species from the John Day formation. 
The posterior protuberance has the same relative size as in A. crasswm. The anterior 
mental foramen is rather small and is placed low down on the mandible, opposite 
the anterior face of Py. ‘The posterior mental foramen is higher up upon the mandi- 
ble and is opposite the posterior face of Pz. 
