24C 
TERTIARY YERTEBRATA OF THE FAYCM. 
of the (\\occi])ital is separated from the ventral portion which joins the basioccipital 
By a rounded notch, which seems to have formed the hinder border of the foramen 
lacerum j>osterms. Close to the inner angle of this notch tlie body of the bone is 
l)erroratcd by the condylar foramen, the inner opening of which is on the inner face 
of the base of the condyle. 
The su])raoccipital [soc.) forms the whole of the upper part of the occipital surface ; 
it is gently concave from side to side, and in the middle line bears a vertical ridge 
which increases in height towards the upper border, but stops short before reaching it. 
'fhis bone, together with the parietal, forms the upper part of the extraordinarily 
developed lambdoidal crest, the two bones sometimes uniting in a suture as much 
as 5 cm. deep. The lateral portion of the crest for a short distance is formed by the 
supraoccipital alone, which here extends on the side of the skull, forming part of 
the posterior end of the temporal fossa?. Beneath this the bone joins the squamosals 
and by its ventral border the exoccipitals. 
The hasioccipital {hoc.) is a very broad bone, probably forming the ventral angles 
of the occipital condyles. Its dorsal (cranial) surface is convex from side to side, the 
ventral concave. In front near its point of union with the basisphenoid the bone 
widens out and bears on its outer angles a pair of large roughened tuberosities 
which project outwards and downwards. 
The hasisj)henoi(I is a very broad flat bone, uniting with the basioccipital behind 
in a long straight transverse suture. liaterally the boundaries of the bone are obscure ; 
probably it imited with the lower end of the alisphenoid, but if so the suture is 
completely obliterated : behind this it unites in a complicated suture with the 
squamosal just internal to the inner end of the articular surface for the mandible. 
In front the bone is overla])ped on either side by the posterior ends of the pterygoid, 
which runs back to about the level of the glenoid surface. 
'Yhe parietals (/)«.) form the roof of the strongly compressed cranial portion of the 
skull. Posteriorly they unite with the supraoccipital in a very deep suture, forming 
the upper part of the lambdoidal crest: in the middle line they join one another also 
in a very deep suture to form the high sagittal crest. The cranial region, though 
very narrow, is somewhat more inflated than in Z. osiris, and beneath the sagittal 
crest is gently convex from above downwards. Veutrally these bones unite with the 
portion of the supraoccipital which ajipears on the hinder wall of the tenijioral fossa, 
and in front of this with the squamosal in a suture running downwards and forwards ; 
the antero-ventral angle of the parietals forms a blunt projection apjiarently for musclc- 
attachnient. The union with the frontals occurs about 3 cm. behind the great 
supraorbital expansions of those bones ; the suture is a complex one, but, speaking 
generally, it runs first downwards, then downwards and backwards. In this region both 
the ])arietals and frontals are enormously thickened. 
'I'he frontals {j'r.), as just mentioned, unite in a complex suture with the parietals, 
