THE SKULL OF PALEORHINUS I4I 
condyle. The relations with the basisphenoid have already been 
mentioned. It is evident from the oblique position of the condyle 
that the animal held its head at an obtuse angle with the body, 
very much, probably, as Dr. Holland has figured the dinosaur Dzplo- 
docus carnegiei in Fig. 1 of his paper on the osteology of Diplodocus. 
The exoccipitals form a little of the condyle, most of the floor and 
all of the side walls of the foramen magnum, but unlike the condition 
in the crocodiles and dinosaurs they are widely separated above as 
in Amblyrhynchus and the mosasaurs. Outwardly they have a sub- 
circular cross-section and distally give rise to the long, flattened 
paroccipital processes which buttress the under surface of the skull 
and along which the inferior part of the quadrate is attached for some 
distance. The inferior processes of the parietals probably touch the 
exoccipitals along their upper edges for some distance. 
The supraocci pital is roughly triangular as seen from above, with 
the apex anterior, and all three sides slightly concave. Its upper sur- 
face is also quite concave and slopes backward rather steeply. It 
forms a floor for the anterior part of the deep median sinus previously 
mentioned. The bone has a width across its base of two and one- 
fourth inches and its length along the median line is about one and 
one-half inches. It unites with the exoccipitals by horizontal sutures 
and thickens along its margins to unite with the parietals in strong 
vertical sutures. | 
OPENINGS ON THE UNDER SURFACE OF THE SKULL 
Internal nares.—These are the most anterior openings on the 
palatal surface. Unfortunately they have been almost obliterated 
in the crushing which the skull has undergone and only the posterior 
portion of one naris is now visible. ‘This has a width of about five- 
eighths inch. Its probable anterior dimensions are indicated in the 
figure. The length cannot be greater than two and one-fourth 
inches and may be somewhat less than this. The nares are separated 
by the vomers, which also form part of their posterior borders. ‘These 
are continued by the pterygoids, and the palatines enclose the open- 
ings on the sides. The vomers are thought to form the anterior 
borders. ‘The internal nares are not, like those of Belodon, placed 
beneath the external, but lie entirely behind them. The anterior 
