1’EKTIAHY VERTEliRATA OF THE FAYCM. 
24 G 
of the exoccipital is separated from the ventral portion which joins the basioccipital 
hy a, rounded notch, wliicli seems to have formed the hinder border of the foramen 
lacerum 2 ^osUrms. Close to the inner angle of tliis notch the body of the bone is 
])erforated l)y the condylar foramen, the inner opening of which is on the inner face 
of the base of the condyle. 
The svjmaoccijntal [soc.) forms the whole of the upper ]iart 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 np])er border, but sto})s short before reaching it. 
'I'his 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 fossm. Beneath this the bone joins the squaraosals 
and by its ventral border the exoccipitals. 
The hasioccijiital {hoc.) is a very broad bone, probably forming the ventral angles 
of the occipital condyles. Its dorsal (cranial) surhice 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. 
'I’he basisphenoid is a very broad flat bone, uniting with the basioccipital behind 
in a long straight transverse suture. Laterally the boundaries of the bone are obscure; 
probably it united 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 overlapped on either side by the posterior ends of the pterygoid, 
which runs back to about the level of the glenoid surhrce. 
The {'pa.) form the loof 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., Ventrally these bones unite with the 
portion of the siijiraoccipital which ap])ears on the hinder wall of the temporal fossa, 
and in front of this with the squamosal in a suture running downwards and forwards ; 
the antero-veutral angle of the })arietals forms a blunt projection a|)))arently for muscle- 
attachment. The union with the frontals occurs about o cm. behind the great 
supraorbital expansions of those bones; the suture is a conqilex one, but, sjieaking 
generally, it runs first downwards, then downwards and backwards. In this region both 
the parietals and frontals are enormously thickened. 
The frontals {jr.), as just mentioned, unite in a complex suture with the parietals. 
