AESINOITHEEIUM. 



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. Behind 

 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 the swollen alveolar mass of the bone. 



Text-fig. 4. 



Skull of Arsinoitherium zitteli : side view of orbital region with the zygomatic arch removed. 



aZ.c, alisphenoid canal; a.o./., antorbital foramen; 5.v., impressions of blood-vessels; e.a.m., external auditory 

 meatus ; /., ? vascular foramen ; f.h., frontal horn ; f.l.a., foramen lacerum anterius ; fr., frontal • 

 ju., jugal ; I., lachrymal ; m.2, m. 3, molars ; mx., maxilla ; on.f., orbito-nasal foramen ; pa., parietal ■ 

 pgl., postglenoid process ; pi., palatine ; p.p.f-, posterior palatine foramen ; p.p.rj., posterior palatine 

 groove; j)t., pterygoid; piy., post-tympanic process; sg'., sq^uamosal; st.r., supratemporal ridge; 

 <./., temporal fossa ; ii., optic foramen. \ nat. size. 



'Wxe jugal (PI. I., PL 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 descriptibn 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 



