POSITION AND STRUCTURE OF HORSE 21 



(elotheres) have still longer and narrower skulls 

 than the horse, yet all the teeth are brachyodont, or 

 short-crowned. Again, the elephant has extremely 

 elongate, or hypsodont, molar teeth, yet it also 

 possesses the shortest skull known among the 

 Mammalia." 



Another feature in the skull of the existing 

 members of the horse family is the comparative 

 shortness of the slit separating the front end of the 

 nasal bones, which form the roof of the nose- 

 chamber, from those of the upper jaw, as is well 

 shown in the figure of the skull of a shire horse 

 (pi. iv. fig. i). The importance of this feature 

 will be apparent when the extinct relatives of 

 the horse are taken into consideration in a later 

 chapter. 



Much has been made of the degree to which the 

 facial portion of the skull of the horse is inclined to 

 the basal axis of its hind part.^ Although there is 

 undoubtedly great variation in this respect between 

 different horse-skulls, it is far from certain that they 

 are really of any special importance. For it has 

 been suggested that this bending down of the fore- 

 part of the skull on the basal axis, which occurs in 

 many grass-eating mammals, is primarily due to 

 the "pull" or strain caused by the act of grazing ; 

 and if this be really the case, it is obvious that 



* See J. C. Ewart, Trans. R. Soc. Edutburgh, vol. xlv. pp. 555, 

 587, 1907- 



