riiOZEUGLODON. 
240 
Internal to the articnlar surface, the squamosal unites in suture witli the alisphenoid, 
and appears to send down a flange of bone which helped to su])port the great swollen 
ipnpanic. This element is badly preserved in the available specimens, but it can be 
seen that it formed a great egg-like expansion with very thick walls and seems to 
be obscurely divided into a small postero-internal lobe and a very much larger outer 
one ; it is wedged in between the scjuamosal on the outer side, the basioccipital and 
(1) 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 
exoccipital 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 
wing of bone, which unites behind with the parietal and above with 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.), which runs forwards and 
upw^ards, the upper edge of the groove being apparently formed by the lower border 
of the frontal and its floor by the orhi to sphenoid {os.). The lower part of the anterior 
edge of the alisphenoid seems to unite with the posterior edge of the orbital plate 
of the palatine, which takes a large share in the formation of the side wall of the skull, 
and along its upper edge overlaps the orbitosphenoid. To the inner side of and 
slightly below the level of the orbit there is a large orbito-nasal (spheno-palatine) 
opening (PI. XXL fig. 1 d, o.nf.), which appears to perforate the orbital plate of the 
palatine and communicates with the nasal passage. 
The foramina of the skull are not well seen. There is a distinct condylar 
foramen in the exoccipital. The foramen lacerum posterias probably occupied the 
interval between the basioccipital and exoccipital and the tympanic. The lower 
end of the alisphenoid is perforated by a foramen which may be equivalent to the 
foramen ovale. The foramen lacerum anterius and the optic foramen must have 
opened behind the edge of the alisphenoid at the bottom of the deep groove which 
runs forwards to the orbit as above mentioned. The relations of the lower part of 
the palatines and the pterygoids cannot be made out. 
From the above description it will be seen that the skull in Vrozeuglodon differs in 
no important particulars from the skulls of iProtocetus atavus and Zeuglodon osiris, 
so well described by IJrs. E. Fraas and Stromer respectively. It is, in fact, in some 
ways intermediate between the turn, as, for instance, in the position of the nares. 
Th us, if the total length of the skull be taken as 100, then in Protocetus (assuming 
2 K 
