ARSINOITIIElilUM. 
13 
frontal, and behind tliis 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. Behind 
this again the maxilla joins the orbital portion of the ])alatine in a suture running 
backwards some distance till it disappears in the depression marking the inner side 
of tlie swollen alveolar mass of the bone. 
Text-fig. 4. 
Skull o£ Arsinoitherium zitteh : side view of orbital region with the zygomatic arch removed. 
alisphenoid canal; a.o./., antorbital foramen; i.v., impressions of blood-vessels; external auditory 
meatus ; /., ? vascular foramen ; f.h., frontal horn ; f.l.a., foramen lacerum anterius ; fr., frontal ; 
ju., jugal ; 1., lachrymal ; m. 2, m. 3, molars ; mx., maxilla ; on.f., orbito-nasal foramen ; pa., parietal ; 
postglenoid process; palatine; p-pf-, posterior palatine foramen; p.p.cj., posterior palatine 
groove ; pt., pterygoid ; ply-, post-tympanic process ; sq., squamosal ; st.r., supratemporal ridge ; 
tf., temporal fossa ; ii., optic foramen, p nat. size. 
jugal (PI. I., PL III. figs. 1, ‘lK,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 
