EOSIEEN LIBTCA. 201 



border of the narial opening. This aperture is an elongated oval in outline, its long 

 diameter being about twice its width. In front of it the upper surface of the rostrum 

 is broad and rounded from side to side, but towards its extremity it becomes compressed 

 and its upper border forms a sharp angle. At the end of the premaxillae there is a pair 

 of large though comparatively shallow sockets for the enlarged incisors (i. 1), separated 

 by a thin wall of bone. Behind and beneath these the alveolar border forms a sharp 

 edge continuous with that of the maxillae. The palatal surface of the premaxillae is 

 strongly arched and posteriorly forms the roof of the large anterior palatine foramen 

 (PI. XX. fig. 1 A, a.p.f.), the lower border of which, as already mentioned, is formed 

 by the anterior edge of the maxillae. Posteriorly the palatine foramen opens into the 

 narial cavity ; its form and relations differ somewhat from those of the same opening 

 in Manatus, Halicore, and Ehytina. In Manatus the palatal portions of the premaxillae 

 are scarcely at all developed ; in Halicore they are in the same plane as, and unite 

 with, the palatine plates of the maxillae, the lateral borders of the elongated anterior 

 palatine foramen being formed equally by the two bones. In Mhytina the elongated 

 foramen is almost entirely enclosed by the premaxillae ; in the present genus it 

 approximates much more nearly to the condition seen in Halitherium, in which, 

 however, the palatine region of the premaxillae is rather less developed. 



The vomer seems to be much like that of Ealitherium, as figured by Lepsius ; it is 

 deeply grooved and the nasal opening must have been divided, at least posteriorly, by 

 a vertical cartilaginous septum. 



In all the specimens the zygomatic arch is broken and incomplete. Judging, 

 however, from an imperfect specimen, it appears that the structure was much as in 

 Halitherium, the zygomatic process of the squamosal forming a broad blade, the lower 

 edge of which is underlain by the backward process of the jugal. This latter 

 widens out in its middle region and bears a downwardly-directed blunt process, as 

 in Halitherium. The body of the squamosal forms a considerable portion of the side 

 wall of the cranium. Posteriorly it unites with the supraoccipital above and perhaps 

 for a short distance below this with the exoccipital ; but for the most part it is separated 

 from the latter bone by the mastoid portion of the periotic, which is exposed on the 

 occipital surface as an elongated convex mass. In front of its union with the mastoid 

 the squamosal bears a strong rounded ridge, forming the outer portion of the lambdoidal 

 crest. In front of this there is a concave surface bounded in front by the ridge marking 

 the origin of the zygomatic process. 



The base of the skull is for the most part wanting ; in the type specimen, however, 

 it can be seen that the basisphenoid and presphenoid were both much thickened and 

 that the former is embraced by the upper ends of the massive pterygoids. 



The cast of the brain-cavity (text-fig. 65) is of considerable interest. The olfactory 

 lobes [ol.) are small and situated low down. The hemispheres are divided from one 

 another by a very deep groove in front, and each is divided into a swollen anterior 



2d 



