PETERSON: A REVISION OF THE ENTELODONTIDAL 91 
compared with some of the large species (Pelonax ramosum) from the upper Oligocene. 
In the latter form these knobs on the lower jaws are particularly long and heavy, 
indicating with other peculiarities a diverging line at that time. In Dinohyus the 
alveolar border has a rapid outward turn at the canine to accommodate the enormous 
root of that tooth. The chin is square and the symphysis shows no mark of division 
between the two rami. There are two mental foramina: the anterior, which is the 
larger, is situated below P*; and the posterior below Ps. The ascending rami are 
low and rapidly flare outward in order to meet the widely separated glenoid cavities 
of the squamosals, which is a peculiarity most nearly approaching what is observed 
in Hippopotamus. ‘The condyles are greatly convex antero-posteriorly and their 
transverse diameter is considerable ; they are only very slightly elevated above the 
alveolar border. The coronoid process is low, but broad, and its free end terminates 
in an enlarged truncated rugosity. The temporal fossa is deep and extends across 
nearly the entire antero-posterior face of the ascending ramus, but does not reach 
very low; its inferior border is developed into a heavy ridge, which unites with the 
base of the condyle externally. The dental foramen is of rather small size and is a 
little posterior to the middle antero-posterior diameter of the sigmoid notch and on 
a level with the alveolar border. 
The hyoidean arch of Dinohyus hollandi is represented by a number of frag- 
ments and three very nearly complete bones, the stylohyoid and both ceratohyals. 
Fia. 34. (1) Inner View of Right Ceratohyal ; (2) Inner View of Stylohyal ; (3) External View of Stylohyal. 
Belonging to type of D. hollandi Peterson. Nat. Size. (Carn. Mus. Cat. Vert. Foss., No. 1594. ) 
The different bones appear to be of somewhat smaller proportions than in Archexo- 
therium ingens described by Professor Scott. ‘The shaft of the stylohyoid is a sinuous 
rod with prominent and spiral ridges (of which one extends the entire length of the 
