THE STRUCTURE AND RELATIONSHIPS OF ANCODUS. 469 
gives it a very different appearance from the regular, almost spherical bulla of 
Eporeodon. As in that genus, the bone is thin, though dense, and the cavity is free 
from cancellated tissue. The auditory meatus is a quite elongate and incomplete 
tube, lacking the dorsal wall. 
^ The cranial foramina cannot be determined in the French skulls, but in the 
White River specimens they are nearly all plainly shown. The optic foramen is 
small and placed rather far forward. The foramen laceruin anterius is quite large 
and irregular, somewhat as in the deer, though smaller. The foramen ovale pene- 
trates the root of the pterygoid process of the alisphenoid, which extends to a con- 
tact with the auditory bulla. The foramen laceriim medium is concealed in the 
deep space enclosed between the bulla and the alisphenoid. The foramen lacerum 
posterius is a narrow slit between the auditory bulla and the basioccipital, while the 
stylomastoid foramen is large and conspicuous. The glenoid foramen is rather in- 
ternal to than behind the postglenoid process. The condylar foramen occupies 
much the same position as in Cariams, but lies a little farther forward, and hence 
is not so much concealed by the overhanging of the condyle. The posterior palatine 
foramina are not placed in the neighborhood of the maxillo-palatiue suture, but 
perlbrate the palatine plates of the maxillaries on a line with the last premolars. 
They' occupy the same position in Oreodon and in Protoceras they are even more 
advanced. The infraorbital foramen is large and opens above p!, while the supra- 
orbital foramina open on the surface of the skull near to the median line. 
The mandible displays considerable differences among the various specimens from 
the upper beds. In one individual the horizontal ramus is thick and heavy, but 
quite shallow vertically, and thus appearing to be quite slender, when viewed from 
the side. The symphysis is procumbent, and its lower border is raised but little 
above that of the rest of the horizontal ramus. The coronoid process is rather short 
and slender, very decidedly recurved, and separated from the condyle by a broad 
sigmoid notcl,. In other specimens, which may represent different species, he 
horizontal ramus is considerably deeper and heavier and he "3' 
abruptly to the proenmbent ohin, the inferior margin of wliieli lies 
higherleveltliantliatoftheotherpartoftheranius. ^ 
the an-le more prominent, the coronoid process much higher and broadei and k s 
strongly recurved, which, renders the sigmoid notch narrower and ess -loop T me s- 
The aUgle is more prominent « prodnced^h*w the ^^vel 
ramus, and the masseteric fossa is >”8“ ,ide the articular 
condyle is much extended transverse y, an ^ r , facet for the postglenoid 
snrfiteC is reflected over npon the tl e mSu ar rami aif some- 
process of the squamosal. In aged individuals the two maiiui 
times an kylosed. _ „+ra+ka+nfrd«rfif/«^withriianifolddifrer- 
has a mandible of similar yp the very much shorter horizontal 
ences of detail. Of these the most striking . tlm j i 
portion, without diastemata, coirespon § abruptly back of the condyle, but 
whole facial region. The angle projects more abrup ) 
