POSITION AND STRUCTURE OF HORSE 23 



a very trivial one, but it happens, as will be noticed 

 more fully in the sequel, that the skulls of certain 

 extinct horses show a much more marked de- 

 pression in the same region — a hollow so deep 

 that it deserves the name of pit rather than 

 depression. 



Writing of this preorbital hollow in the extinct 

 three-toed Ilipparion, Sir W. H. Flower in his 

 volume on The Horse,^ observed that "although 

 such a pit is not found in any of the existing 

 species of horse, it was not infrequent in many 

 extinct forms, and varied in them in size and depth. 

 It so closely resembles a similar depression found 

 in the same situation in many species of deer and 

 antelopes, which lodges a glandular infolding or 

 pouch of the skin called the 'suborbital gland,' 

 •crumen,' or in French 'larmier,' that there can be 

 little doubt but that it had the same purpose in the 

 hipparion. This gland in the existing animals that 

 possess it secretes a peculiar oily odorous substance, 

 the scent of which enables the animals provided 

 with it to recoenise each other even at immense 

 distances, the faculty of smell being also developed 

 to a wonderful degree. . . . 



" The presence of this gland in the hipparion 

 and its absence in the more modern Equidce has 

 been given as a reason for supposing that the 

 latter are not the direct descendants of the former, 



^ London, 1891, p. 64. 



