PETERSON: A REVISION OF THE ENTELODONTID& 87 if 
well back in the skull, the face is very long, and the brain-case short. There is a 
well developed sagittal crest, and an overhanging occiput.” The descending broad 
and thin plate below the orbit is quite small when compared with some Oligocene 
species, and the zygomatic process of the jugal terminates in a heavy buttress, which 
forms the anterior border of the glenoid cavity. The comparatively gentle down- 
ward sweep of the angle of the lower jaw and the relatively small process on the 
ventral border of the chin are other features of importance. 
The base of the skull has received considerable injury by crushing, and the 
sutures are entirely closed, but the character of the different bones are generally simi- 
lar to, and agree quite closely with, the descriptions of those of the American Entelo- 
donts given by Professors Leidy (44, pp. 57-67), Scott (87, pp. 278-287), and others. 
The basioccipital is short, slightly keeled ventrally, and hasa rough area at its junc- 
tion with the basisphenoid. ‘The condylar foramen is of considerable size, and, as 
in A. mortom, is placed some distance in front of the condyle. The exoccipital has 
a great transverse diameter at the base of the occiput and narrows rapidly superiorly. 
The condyles are well separated by broad notches superiorly and inferiorly, and their 
transverse diameters are a little less than three-fifths greater than the vertical, which 
agrees better with the American species than with Hntelodon magnum of Europe. 
The foramen magnum is transversely oblong in a greater degree than is the case in ; 
the Princeton specimen, but this may in part be due to crushing. The paroccipital 
process is quite heavy, trihedral in cross-section, and terminates in a truncated and 
rugose free end; its position is similar to that in Archexotherium mortoni figured by 
Professor Scott (87, Pl. XVIII, fig. 2), but apparently relatively shorter. 
The stylomastoid foramen and the pit for the tympano-hyal occupy apparently 
the same relative positions as in the Oligocene genus (see P]. LVII), 7. ¢., anterior 
and external to the condylar foramen. The superior wing-like processes of the 
supra-occipital are crushed laterally, but I judge that in their normal condition they | 
assume characters similar to the American forms generally. The basisphenoid, as in 
Archeotherium ingens, is narrow and not keeled ventrally. There is a canal in the 
median line, just at the point where the basisphenoid is concealed by the union of 
the palatines and pterygoids; this is also present in A. mortoni and has been figured 
by Scott (J.¢., Pl. XVIII, fig. 1). Whether or not there was a tympanic bulla in Dino- 
hyus cannot be determined from the material at hand. The pterygoids are much com- 
pressed laterally, but they extend well down and terminate in short and backwardly 
directed hamular processes. ‘The foramen ovale is of considerable size and occupies i 
5 This overhanging of the occiput in the type is due, to some extent, to crushing. 
35 In a well preserved skull of Dinohyus hollandi collected in the Agate Spring Quarries (University Hill Quarry) 
by Professor Barbour in 1908, there are no tympanic bull. 
