560 ARCHAOTHERIUM OF NEBRASKA. 
The face is elongated, as in the Hog, but is not compressed laterally, as in 
Hyracotherium, but is demi-cylindroid, narrowing anteriorly. 
The nasal bones extend as far back as to be on a line with the anterior margin 
of the orbit. They very gradually increase in breadth for two inches from behind, 
and then again gradually decrease. They form a continuous convexity with the 
maxillary bones. The frontal projects between the latter and the former, on a line 
with the posterior surface of the last premolar. The malar and lachrymal bones 
advance upon the face to about half an inch of the same line. 
The hard palate is strongly arched from side to side. 
ADMEASUREMENTS. 
Inches. 
Estimated length of line of posterior five molars, . , , ; 4} 
Distance between the second true molars, . : : : ‘ 13 
Height of face on a line with the last premolar, . gh cine : 3 
Height on a line with the second true molar, ‘ , 4 
Breadth of face above the second true molar, , ‘ , ‘ 3} 
The species was dedicated to the late Dr. Samuel George Morton, formerly 
President of the Academy of Natural Sciences of Philadelphia, and author of 
Crania Americana, Crania Egyptiaca, etc. 
Since writing the preceding description of the specimens upon which were esta- 
blished the Archzotherium Mortoni, I have had an opportunity of examining an- 
other and very important fragment of the same animal, which until now had not 
arrived from Dr. Owen’s residence in Indiana. It belongs to the same collection 
of Nebraska fossils which form the basis of this part of Dr. Owen’s Report. The 
specimen consists of the greater portion of the cranium proper, the right side of 
which is nearly entire, part of the forehead and face without the nasal bones and 
anterior extremity, and portions of both sides of the lower jaw (Tab. x., 1-3). It 
belonged to a young animal, as the sutures generally are separable, and the tempo- 
rary teeth had not yet been shed. 
In the upper jaw (Tab. x., fig. 1) of the specimen upon the right side are pre- 
served in place the second and third temporary molars, and the three permanent 
true molars, the last of which still remained concealed within the jaw. On the 
other side the posterior permanent premolars have been exposed, and the anterior 
two permanent molars are in place. In the fragment of the right side of the lower 
jaw (Tab. x., fig. 2) a portion of the last temporary molar and the first permanent 
molar are preserved, and a part of the last permanent premolar is observed within 
the jaw at its anterior broken extremity. The other fragment (Tab. x., fig. 3) 
very much crushed, contains the three permanent true molars, the last of which 
had not yet protruded, a portion of the last temporary molar, and the last perma- 
_ nent premolar, which is partially exposed at the broken end of the specimen. 
The skull (Tab. x., fig. 2) is quite peculiar i in its form from that of any existing 
animal, and among om extinct species was probably most like that of Choero- 
potamus, to which Archzotherium is very closely allied. The cranium proper, in 
the great extent and general form of the temporal fosse, separated by a high sagittal 
