ARSINOITJIEKIUM. 
13 
frontal, and behind this appears to form the ventral edge of an elongated orbito-nasal 
foramen (text-fig. 4., on.f.), opening from the orbit into the nasal passage, llehind 
this again the maxilla joins the orbital portion of the palatine in a suture running 
backwards some distance till it disappears in the depression marking the inner side 
of tlic swollen alveolar mass of the bone. 
Text-fig. 4. 
Skull of Arsinoitheriicm zitteli : side view of orbital region with the zygomatic arch removed. 
a4r., alispheuoid canal; a.o./., antorhital foramen; 6.r., impressions of blood-vessels ; external auditory 
meatus ; ? vascular foramen ; fJi., frontal horn ; f.l.a., foi-amen lacerum anterius ; fr., frontal ; 
ju., jugal; 1., lachrymal; m. 2, m. 3, molars; mx., maxilla; on.f., orbito-nasal foramen; pa., parietal ; 
injl., postglenoid process; pi., palatine; p.p./., posterior palatine foramen ; p.p.^r., posterior palatine 
groove ; pt., pterygoid ; pty., post-tympanic process ; sq., squamosal ; st.r., supratemporal ridge ; 
t.f., temporal fossa ; ii., optic foramen. \ nat. size. 
The jugal (PI. I., PI. III. figs. 1, 2 k,ju.) articulates in front with the malar region of 
the maxilla by a long process which runs up as far as the anterior angle of the orbit, 
where it meets the lachrymal and completely excludes the maxilla from the margin of 
the orbit, as already mentioned in the description of that bone. Immediately below 
and in front of the orbit there is a very prominent, rough, curved ridge (marked ju. in 
text-fig. 4) which projects considerably from the side of the face and must have served 
