114 Dr. C. W. Andrews — Notes on Egyptian Eocene Mammals. 



and probably with the auditory meatus by several foramina. The 

 swelling of the back of the head has not yet gone far enough to lead 

 to the disappearance of the sagittal crest, which is fairly prominent, 

 and divides anteriorly into the temporal ridges, which run out 

 on to the post-orbital processes of the frontals. The nasals are 

 short, and their relations to the surrounding bones much as la 

 Eleplias. The nasal opening has already been shifted back 

 a considerable distance behind the anterior end of the snout, but 

 not to the same degree as in the elephants, since it is still in 

 front of the anterior border of the orbits, while in the later 

 forms it has come to lie behind it and at the same time looks more 

 upwards. The premaxillaries have exactly the same relations to 

 the nasal opening and to the neighbouring bones as in Elephas, but 

 the form of their anterior portion is quite different, owing to the 

 fact that the tusks are still small, so that the great alveoli and 

 the broad truncated anterior border of these bones, so characteristic 

 of the elephants, are here unnecessary, and they terminate anteriorly 

 almost in a point. The maxilla is greatly elongated. It bears 

 a stout zj'gomatic process, the base of which is perforated by 

 a large antorbital canal, which opens on the face by two foramina. 

 The lachrymal is exactly as in Elephas. The jugal is large, and 

 extends from the orbit back beneath the zygomatic process of the 

 squamosal as far as the glenoid surface for the mandible. The 

 cranial portion of the squamosal is considerably swollen by the 

 presence of air sinuses ; it completely surrounds the auditory 

 opening, sending down behind it a post-tympanic (p.t.) process. The 

 articular surface for the mandible is very large ; it is slightly 

 concave from side to side, and very convex from before backwards; 

 the mandible must have much freer play both from side to side and 

 up and down than in the recent elephants. The alisphenoid is 

 perforated by an alisphenoid canal (al.c), and sends down on to the 

 pterygoid a pterygoid wing {al.pt.), the anterior edge of which 

 forms the outer border of a deep groove, which is continued upwards 

 and forwards towards the post-orbital process of the frontal. At the 

 bottom of this groove are the anterior oiJenings of the alisphenoid 

 canal, the foramen lacerum anterius and the optic foramen, as in 

 Elephas. The tympanic is small, less inflated than in the later type, 

 and does not extend into the mandibular articulation. 



There is no distinct condylar foramen ; it appears to be confluent 

 with the foramen lacerum posterius. The opening of the internal 

 nares is higher than wide; the maxillae, palatines, and pterygoids 

 which form its side walls are all to some extent thickened by the 

 development of coarsely cellular bone, which is particularly 

 abundant in the portion of the maxilla immediately behind the last 

 molar. The axis of the palate is somewhat bent up with regard to 

 the basi-cranial axis, so that the two make a very obtuse angle with 

 one another: in the elephants this character is carried still further. 



The limb bones of Palaomastodon are comparatively rare, most 

 of the very large number of bones now collected belonging to 

 Arsinoitheriiim. Such specimens as can be referred with certainty to 



