210 TEETIAET VEETBBEATA OF THE FAYtTM. 



opening, and beneath the alveolus-like depression noticed above, there is a rounded 

 mass, which seems to be homologous with the bony capsule in which the successional 

 teeth develop in the Manatee. Probably, therefore, in the mandible at least of the 

 present species, the beginning of a molar succession similar to that seen in the Manatee 

 had already been established. 



Lotver Dentition. — In no specimen are the lower teeth well preserved, and in the 

 most nearly complete example there are only three greatly worn and broken molars 

 in situ. The following account of the lower teeth is therefore deduced merely from 

 the alveoli in the jaw figured on PI. XX. figs. 2, 2 a, and, when more satisfactory 

 specimens are found, may have to be revised. In the downwardly turned alveolar 

 surface of the symphysial region there are four pairs of alveoli, probably indicating 

 the existence of three pairs of incisors and a canine. The most anterior pair of 

 sockets are shallow and not very well defined, so that not improbably the anterior 

 tooth was deciduous, and its place covered with a horny sheath as in Manatus and 

 probably Halitherium. On the other hand, the remaining three pairs of alveoli are 

 so deep and sharply defined that most likely their teeth were functional. Behind 

 these symphysial alveoli come thirteen others, increasing in size from before backwards. 

 The posterior six sockets undoubtedly bore three double-rooted molars (as can be 

 seen in another specimen), and the remaining seven probably belonged to three 

 anterior single-rooted teeth (? premolars) and two posterior double-rooted teeth. If 

 this interpretation be correct, the dental formula of this mandible is i. 3, c. 1, 'pm. 3, 

 m. 5, regarding the double-rooted teeth as molars. As mentioned above, it seems 

 not impossible that the number of molars would subsequently be added to from 

 behind. 



The only lower molars available for examination are greatly worn, but seem to 

 have consisted of a pair of transverse crests and a small posterior talon. 



Mandible of Eotherium. — A mandible (text-fig. 67) from the white limestones of 

 the Mokattam Hills probably belongs to the same species and perhaps to the same 

 individual as the skuU above referred to Eotherium oegyptiacum. It differs very little 

 in form from the mandible of JEosiren, having the same strongly deflected anterior 

 region; the symphysis {sym.)' is greatly thickened, though much less so than in 

 Uosiren. The chief difference between the two is that the alveoli of the anterior 

 teeth are better marked. Unfortunately, only the three molars are present, and 

 the interpretation of the dentition from the alveoli is open to much uncertainty. 

 The three pairs of incisors were large teeth, the anterior ones (i. 1) being in contact 

 with one another in the middle line, and directed almost forwards. On the upper 

 surface of the symphysis between the alveoli of the second and third pairs of incisors 

 {i. 2, i. 3) and of the canines (c.) is a rough surface which was probably covered 

 with the horny substance which eventually displaced and replaced the teeth. A little 



