564 PROFESSOR J. C. EWART 



this is a primitive condition, and that the Forest variety in having the face, on reaching 

 maturity, nearly in a line with the cranium, is more specialised than the Steppe horse in 

 which the face is as strongly bent downwards in the adult as in the foal. If in the 

 Steppe horse the bent condition present in the foal persisted up to adult life, some 

 support would be given to this view ; but when it is mentioned that in the Steppe horse, 

 as the foal grows older, the face is gradually unbent, it will be evident that the Steppe 

 variety is eventually the more highly specialised. Owing to the gradual unbending 

 during the first year, the skull of a fifteen months Prejvalsky's horse (PL I. fig. 5) very 

 closely resembles the skull of an adult Forest horse (PL I. fig. 2). But during the 

 second year the face again begins to bend downwards in the Steppe horse, and the 

 bending continues until it forms a well-marked angle with the cranium (fig. 1). If the 



Fig. 1. — Lateral view of the skull of a Prejvalsky stallion (age about 3 years 8 months). The face is bent downwards on 

 the cranium, and the post-orbital part of the skull, as in the deflected Roman skull (PI. II. fig. 7), is relatively short. 

 There is a slight prominence below the level of the orbits, such as often occurs in Shire horses, and the nasals are long and 

 bent downwards at the tips. The outline of the face, instead of being concave as in the Forest horse, is convex ; in 

 some cases the curvature is more marked than in the skull figured, and the premaxillse are longer and bent down on the 

 maxillae. The difference in the facial outline between old and young Steppe horses is due to an expansion of the frontal 

 sinuses and to an increase in the depth of the nasal fosste. The increase in the length of the orbit has probably resulted 

 from the articular surfaces for the mandible having been shunted backwards. Skull of horse in fig. 12, PI. III. 



bending of the face on the cranium has, as seems probable, been effected very 

 gradually (since forests and marshes were abandoned for a free life in open plains and 

 uplands), it follows that the Steppe variety branched off' from the common stem at a 

 very remote period.* It is especially worthy of note that the Steppe horse, in having 

 for a time a nearly straight skull, repeats during its growth one of the most striking 

 characters of its remote forest-haunting ancestors. 



The deflected Newstead skulls also differ from skulls of the Forest type in the 

 outline of the face. Between the highest point of the cranium and the most elevated 

 part of the nasal bones, the outline is always concave in the Forest variety, i.e. in the 

 Forest variety the face is dished (PL I. fig. 2). In a yearling Steppe horse the outline 



* In Neohipparion of the Miocene, Hipparion of the Pliocene, and E. Scotti of the Pleistocene, the face is strongly 

 bent downwards on the cranium. 



