220 
CORYPHODON. 
These shallow gutters converge posteriorly, unite at the abrupt termination 
of the median ridge, and continue into the deep notch of the posterior 
border of the skull. The lateral borders of the superior face of the skull 
overhanging the temporal fossae, commence behind the orbits and slope 
obliquely upward and outward. The margin makes an open sigmoid 
flexure, having a long concavity behind the orbit, a convexity just above 
the glenoid cavity, and a slight contraction posterior to that point. They 
project as far backward as the line of the occipital condyles, each side 
forming a prominent angle, separated from the opposite one by an open 
notch. The edge is obtuse and rather thin. The nareal opening is wide, 
and subrouncT in outline. The free portions of the nasal bones are wanting 
in the specimen; but their basis is small, and they were probably insig¬ 
nificant, as in C. lonias. The dentigerous portions of the premaxillary bones 
are obliquely oval in form, the long axis being at 45° inclination to the 
long axis of the skull. The ascending portion extends to the nasal bones, 
although in the specimen the distinguishing suture is invisible. On the 
middle line, they are in contact, but not united by suture; and each sends 
posteriorly a narrow process, which separates each incisive foramen from 
the median line for a distance at least. 
The palatal surface is not narrowed as in LoxolopJiodon cornutus, nor 
very concave. Its widest portion is that between the external incisors; it 
is a little narrower between the canines, and narrower still between the 
molars, whose inner extremities form parallel borders of the palate. The 
contrast between the great contraction behind the canine and the expansion 
of the premaxillary region is striking, and results in a short spatulate out¬ 
line. The posterior extremity of the maxillary bone does not project much 
beyond the posterior base of the zygoma, and is separated by a shallow 
groove from the lamina pyramidalis of the palatine bone. The palatal 
border of the nares is short, and extends forward as far as opposite the 
middle of the inner extremity of the posterior molar. The nareal trough 
is elongate and rather narrow. The pterygoid processes of the sphenoid 
bone commence a little behind the anterior borders of the glenoid surfaces 
and just in front of the foramen ovale. They descend with the posterior 
border directed obliquely forward, and meeting the palatine laminae at an 
