‘200 
TOIM’IAKY A'KIirEIJR VTA OF TIFE FAYCAM. 
by tlu' n])))ai'outly loosely luiited 'periotic {jier.). 'I'lic relations of the bones in tliis 
r('^ion se('in to be; very similar to those fonnd in Manatas, except that in the hitter 
p,-enns llie s(iuamosal is not entirely cut off from contact with the snpraoccipital. 
Jjeneatli the ])('riotic openin'^ the post-tym])anic portion of the squamosal unites 
closidy with the anterior face of the paroccipital region of the exoccipital, and in front 
forms the posterior border of the external auditory meatus, the anterior boundary 
of which is constituted l)y the slightly developed postgienoid process. The articular 
surface {(jl.) for the mandible is very broad ; it is slightly concave from side to side 
and gently convex from before backwards, except where it runs on to the slight ])ost- 
glenoid ridge. The zygomatic process (c////.) is very stout and is triangular in section ; 
it is underlain anteriorly by a slender prolongation of the jugal. The iiarietals [pa.) 
are large bones forming most of the cranial roof; posteriorly, as already mentioned, 
they are separated in the middle line by a process of the snpraoccipital, and laterally 
tlu'y send back processes which thrust tliemselves between the squamosal and 
supraoccipital, and hebr to form the large prominences of the lambdoidal ridge. From 
the ])Ost('rior angles of the bones a pair of not very well-defined snpratemporal ridges 
run forwards, first converging slightly, then running parallel to about the level of 
the anterior border of the glenoid surface; in front of this they diverge considerably, 
and finally become coutinuons with the hinder edges of the postorbital processes 
of the frontals. 
Owing to the comparatively small development of the snpratemporal ridges and 
also to the slight inflation of the cranial portion of the skull, the roof is not nearly 
so sharply marked off from the temporal fossae as in the later forms, even in Eosiren. 
The ventral borders of the parietals unite with the sqnamosals posteriorly, then for 
a short distance with the upper end of the alispltcnoid («/.), and in front of this again 
with the frontals, which they overla]:» in a squamous suture, running forwards in 
a sharji angle on the snpratemporal ridges. The frontals (fr.) are very wide, forming 
the broad gently convex skull-roof in the region of the orbits, which they overhang 
as large supraorbital plates. Posteriorly they join the alisphenoid and in front 
of this their ventral edges seem to form the outer border of the groove for the o])tic 
nerve. Their anterior border is notched for the recejition of the hinder ends of the 
nasals, between which they send a short triangular jiroccss. 'The nasals ijia.) seem to 
have been of considerable size, and overhung the narial o])oning [nar.) to some extent. 
'The o]iening itself is an elongated oval in outline, and its borders are foianed by the 
nasals behind and by the premaxilhe in front and at the sides. 'The premaxillary 
rostrum must have been bent down to a considerable extent, but iii tins s])ecimen it 
has been straightened out by tlie pressure to which it has been subjected, and the end 
has been broken across the alveoli of the anterior incisors. 'The n])])cr surface of the 
rostrum in front of the narial opening is gently concave from side to side. 
'The maxilla (mx.) is a greatly elongated bone ; the anterior edge ot its palatine region 
