THE SKULL, OF THE PREHISTORIC HORSES. A13 

Fig. 491. (a) Teeth of Equus caballus pumpellii. Right part of upper maxilla. 
(b) Teeth of Ass, from the Mummy from Abadieh, Egypt. 
(c) Teeth of Horse, Pile-dwelling of Auvernier (Bronze Age). 
(d) Teeth of Equus przewalskii. 
(e) Teeth of Tscherski’s Siberian Horse. 
The form of the enamel of the teeth deserves further consideration, but 
since in horses the enamel is more wavy in younger than in older animals, while 
in the ass the reverse is the case, only specimens of similar age must be com- 
pared. Frank asserts that in the Oriental horse the enamel plication is less than 
in the Occidental. ‘The most marked enamel plication of the interior borders of 
the anterior islands is shown in the diluvial horses; among these especially in the 
horses of Westeregeln and Thiede. The horse of Remagen has also slighter rip- 
pling, and I find it still less in the horse of Kesslerloch and Solutré. The plication 
