TEETIAET VEETEBEATA OP THE FATtTM. 



"Family AESINOITHERIID^. 

 Comprising only the genus Arsinoitherium, and not yet precisely definable. 



Genus ARSINOITHEEIUM, Beadnell. 

 [Prelim. Note on Arsinoitherium zitteli, Beadn. : Survey Dept., Cairo, 1902.] 



Occipital surface of skull strongly inclined forwards ; a pair of small frontal 

 horns over the orbits, and a pair of enormous nasal horns arising from a common 

 base constituted by the nasals and frontals. In the adult, a prenasal bar of bone 

 uniting the anterior border of the nasals with the premaxillse. Orbit open posteriorly. 

 Palate strongly arched from side to side. Molars bilophodont. Neck very short. 

 Humerus and femur considerably longer than the radius and tibia respectively. 



So far as known, this genus is represented by two species only in the Upper Eocene 

 of Egypt. Nearly all parts of the skeleton have been discovered. 



Skidl (Pis. I., II., III. ; text-figs. 1-4). — The skulls in the collections belong to 

 individuals of various ages, ranging from young animals in which the last molar is still 

 uncut and most of the sutures remain open (PI. III. fig. 2) to fully adult individuals 

 with the last molar much worn and almost all the sutures obliterated (Pis. I., II.). An 

 intermediate condition is shown in PI. III. fig. 1, where the last molar is just coming 

 into wear, and some of the sutures {e. g. that between the exoccipital and squamosal) 

 are still open, while the horns are rounded and the character of the bone shows that 

 growth was actively proceeding at their summit. An adult skull in the British 

 Museum (Pis. I., II.) suffices for the greater part of the general description, and 

 this specimen is important because it was found in actual association with its 

 mandible. 



The general appearance of the skull is most remarkable. Seen from behind (text- 

 fig. 1) the most notable characters are : — (1) The large size and great prominence of 

 the occipital condyles ; (2) the extreme inclination forwards of the occijntal surface ; 

 (3) the great development of the lambdoidal crest, the lower ends of which form strong 

 prominences in the adult animal. In a front view (PI. II. fig. 1 a) the appearance 

 is very curious, the two great horns and the sharp wedge-shaped extremity of the 

 snout giving the whole a triradiate form. Beneath the base of the horns are the 

 two very large narial apertures, divided in the adult by a vertical prenasal bar 

 of bone. An upper view of the skull (PL III. fig. 2) shows the large widely- 

 separated and prominent condyles, the forwardly-inclined occipital surface, and in 



