GENIOHTFS MIEUS. 193 



Family SUID^. 



The peculiar genus Geniohyus may be referred provisionally to this family, 

 of which it may be taken as representing a distinct subfamily, the Oeniohyince. 

 Further knowledge of this remarkable form may lead to the establishment of a new 

 family for its reception, but at present the course here adopted seems best. 



Genus GENIOHYUS, Andrews. 

 [Geol. Mag. [5] vol. i. (1904) p. 160.] 



Known only from the mandible and lower teeth. The dental formula for the 

 mandible seems to be i. 3, c.\, pm. 4, m. 3, but possibly the canine may be wanting, 

 as will be explained below. The anterior incisors are enlarged and procumbent ; the 

 premolars are all simpler than the molars, which are bunodont. The mandible bears 

 on its lower border, immediately behind and beneath the symphysis, a pair of large 

 backwardly-directed processes. 



Three species of this genus are at present known. 



Geniohyus mirUS, Andrews. 

 [Plate XIX. figs. 1, 1 A.] 



1904. Geniohyus mirus, C. W. Andrews, Geol. Mag. [5] vol. i. pp. 160-161, pi. vi. fig. 4. 



Type Specimen. — Symphysis and part of the right ramus of a mandible with the 

 premolars and molars well preserved (PI. XIX. figs. I, 1a); Geological Museum, 

 Cairo. 



This is the smallest of the three species, and at the same time the premolars are the 

 simplest. Length of the premolar series is 5 cm. 



Form. & Log. — Fluvio-marine beds (Upper Eocene) : north of Birket-el-Qurun. 



C. 8634. Symphysis and part of right ramus o£ mandible. Type specimen described and figured loc. 

 cit. supra ; also PL XIX. figs. 1, 1 A. The spout-like symphysial region is narrow both 

 from side to side and from above downwards, and behind it, just where the rami begin 

 to diverge, the ventral border of the jaw is produced downwards and backwards on 

 either side into a long backwardly directed process {pr.), which is oval in section and 

 probably ended in a point, but the tip is broken away. The hinder border of the base 

 of this process is connected with the lower edge of the horizontal ramus by a thin plate 

 of bone. The ramus is incomplete ventrally, but was evidently narrow from above 

 downwards. The function of the peculiar paired ventral process is uncertain. In the 

 Dinocerata a somewhat similarly situated prominence on the mandible helped to protect 



2c 



