192 TEETIAET VEETEBEATA OF THE FAYtTM. 



and are separated both from the incisors "and premolars by long diastemata. In the 

 upper jaw there are four premolars, pm. 1 being separated from pm. 2 by a diastema. 

 The molars have very brachyodont crowns, the cusps being only slightly selenodont 

 but strongly convex on their outer face. The type species is R. valdense. Later, 

 Kowalevsky * described and figured another species, B. fronstettense, in which the 

 upper molars are still more bunodont, the cusps being shorter and thicker; the 

 middle fold of the outer wall {mesostyle) is also more strongly developed, as, judging 

 from the figures, is the cingulum generally. A single tooth from the Upper Eocene 

 of the Fayum resembles those figured by Kowalevsky so closely in its structure that 

 it is here referred to the same genus, though, on account of its much greater size, to 

 a distinct species. 



Rhagatherium aegyptiacum, sp. nov. 



[Plate XVIII. fig. 5.J 



Type Specimen. — Left upper molar, probably the third (PI. XVIII. fig. 5); British 

 Museum. 



The tooth upon which this species is founded , is clearly that of a priinitive 

 Anthracotheroid, in which the selenodont condition of the molars of the later forms 

 is still only indicated, and the cusps are low and strongly convex on the outer as well 

 as on the inner face. There are three main cusps in front and two behind, as usual 

 in the family ; the intermediate anterior cusp is the smallest. The cingulum is well 

 developed round the whole crown, with the exception of the outer face of the 

 postero-external cusp. The fold on the outer face between the main cusps forms 

 a well-developed mesostyle. In wear, the inner cusps would tend to give a V-shaped 

 pattern, but this would not be the case with the outer ones. The tooth differs from 

 those of B. valdense, Pictet, and B. fronstettense, Kowalevsky, by its much larger 

 size, and from the former by its still more bunodont crown. Possibly, when the 

 dentition is fully known, it may be necessary to establish a new genus for this species. 



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



ffi. 8449. Left upper molar, probably the third ; the low cusps are just coming into wear. Type 

 specimen, figured PI. XVIII. fig. 5. The length of this tooth is 1"8 cm.; its greatest 

 width 2 cm. In H. valdense the corresponding measurements are '75 cm. and "8 cm. ; 

 in R. fronstettense they are 1 cm. and 1 cm. 



* "Monographie der Gattung Anthraeotherium, Cuv.," PalsBontographica, vol. xxii. (1876) p. 228, pi. viii. 

 figs. 57, 58. 



