PEOZEUGLODON. 
240 
Internal to tlic articnlar surface, the squamosal unites in suture with tlic alisphcnoid, 
and appears to send down a flange of bone which helped to support the great swollen 
iymiumic. This element is badly preserved in the available specimens, but it can he 
seen that it formed a great egg-like expansion with very thick walls and seems to 
he obscurely divided into a small postero-internal lobe and a very much larger outer 
one ; it is wedged in between the squamosal on the outer side, the basioccipital and 
(?) the basisphenoid on the inner, and the alisphenoid in front. The periotic {per.), 
as already described, appears on the posterior surface of the skull between the 
cxoccipital and the squamosal ; on the inner face of the skull it extends some distance 
upwards. The external auditory meatus opened immediately behind the postglenoid 
process of the squamosal. 
The alisphenoid {al.) must have united at its lower end with the basisphenoid, but the 
suture is obliterated. Immediately in front of the tympanic bulla it is perforated by 
a large foramen, apparently the foramen ovale. Above this it joins and is overlapped 
by the inner end of the portion of the squamosal bearing the articular surface. Above 
this again it runs obliquely upwards and forwards on the side of the cranium as a 
Aving of bone, which unites behind Avith the parietal and above Avith the frontal for 
a short distance. The upper part of its anterior border forms the outer lip of the 
posterior end of the deep groove for the optic nerve [opt.], Avhich runs forwards and 
upAvards, the upper edge of the groove being apparently formed by the lower border 
of the frontal and its floor by the orhito sphenoid {os.). The lower part of the anterior 
edge of the alisphenoid seems to unite Avith the posterior edge of the orbital plate 
of the palatine, Avhich takes a large share in the formation of the side Avail of the skull, 
and along its upper edge overlaps the orbitosphenoid. To the inner side of and 
slightly beloAv the level of the orbit there is a large orbito-nasal (spheno-palatine) 
opening (PI. XXI. fig. 1 n, o.nf.), Avhich appears to perforate the orbital plate of the 
palatine and communicates Avith the nasal passage. 
The foramina of the skull are not Avell seen. There is a distinct condylar 
foramen in the cxoccipital. The foramen lacermn posterias probably occupied the 
interval between the basioccipital and cxoccipital and the tympanic. The loAA'er 
end of the alisphenoid is perforated by a foramen Avhich may be equivalent to the 
foramen ovale. The foramen laceriim anterius and the optic foramen must have 
opened behind the edge of the alisphenoid at the bottom of the deep groove Avhich 
runs foi'Avards to the orbit as above mentioned. The relations of the loAver part of 
the palatines and the pterygoids cannot be made out. 
From the above description it Avill be seen that the skull in Frozenglodon differs in 
no important particulars from the skulls of Frotocetus atavus and Zeiiglodon osiris, 
so well described by F)rs. E. Fraas and Stromer respectively. It is, in fact, in some 
Avays intermediate betAveen the tAvo, as, for instance, in the position of the nares. 
Thus, if the total length of the skull be taken as lOU, then in Frotocctus (assuming 
