Anthracotheres and allied Forms. 



5 1 5 



Gelasmodon gracilis, gen. et sp. n. 



The type-specimen (fig. 1) is a fairly complete mandible of 

 long and slender build, somewhat similar to that found in 

 the genus Ancodon, as, for example, that of Ancodon 

 gorringei*. It presents, however, certain minor differences 

 in general shape and verv pronounced differences in the 

 dentition. 



The mandible has, in the first place, a very marked curve 

 along the lower border, which rises gradually from the point 

 of greatest depth between the second and third molars up to 

 the end of the symphysis. In A. gorringei the border is 

 straighter, sloping up a little from the same point of greatest 

 depth, and then flattening out or even turning down some- 

 what at the symphysis. 



Fig. 1. 



The dentition is peculiar. There is a closed series of three 

 molars and four premolars. A long diastema then separates 

 the first premolar from the next tooth, which is presumably 

 the canine. This tooth is very small and only just cuts the 

 gum; its position is marked by the arrow in the figure. \\\ 

 front of this tooth the alveolar border is exceedingly thin, 

 sharp-edged, and without trace either of teeth or o( any 

 sockets to contain them. It would appear that this animal 

 was toothless in this region or else had the teeth much 

 reduced, as there is hardly enough substance at the edge <»t 

 the jaw to carry an average-sized incisor such as is found 

 in the genus Ancodon generally. The position of the first 

 premolar close against the second is also a point of difference. 



* Andrews, 'Catalogue of the Tertiary Vertebrate of the Fayum' 

 (British Museum). 



