ON SKULLS OF HORSES FROM THE ROMAN FORT AT NEWSTEAD. 563 



The best example of the bent type of skull from the Newstead fort is represented 

 in PI. II. fig. 7. The difference between a relatively straight skull of the Forest 

 type and a skull of the Steppe type is most realised when two such skulls are so 

 placed that the basi-cranial axis occupies a horizontal position. This difference is well 

 brought out in PL II. figs. 6 and 7. In PI. II. fig. 7, which represents a strongly 

 bent Newstead skull, a line carried through the basi-cranial axis emerges between the 

 upper and middle thirds of the nasals, whereas in a skull of the Forest type a similar 

 line emerges well below the tips of the nasals (PL II. fig. 6). I may here mention 

 that there are excellent reasons for believing that a bent skull greatly facilitates 

 feeding on very short herbage. In a sheep, when feeding, the grass is pressed by 

 the sharp-edged lower front teeth against the hard pad attached to the upper jaw ; 

 and then as a rule the head is jerked rapidly forwards, with the result that the 

 grass, held as in a vice, is severed partly by cutting and partly by tearing. 



In the Steppe variety of the horse the grass is seized between the upper and lower 

 incisors, but the head, instead of being invariably jerked forwards — the usual procedure 

 in sheep — is sometimes moved forwards, sometimes backwards, but more frequently 

 from side to side. 



It is especially interesting to note that, in members of the Forest variety, the face 

 at birth is nearly as bent downwards on the cranium as in full-grown members of the 

 Steppe variety. The reason of this may perhaps be that in the case of mammals 

 which suck standing, the milk is obtained more readily when the face is bent down- 

 wards on the cranium. To induce the flow of milk the mammary gland requires to be 

 pressed — at times with considerable force — and this pressure is apparently more readily 

 effected when the face is bent downwards than when in a line with the cranium ; the 

 snout, it need hardly be said, in forms which suck standing, plays the part of the 

 fore-limbs in forms which take their nourishment in a recumbent or sitting attitude. 

 That the downward bending of the face at birth is connected with sucking seems to 

 receive support from the fact that in the very young Giraffe the deflection of the 

 cranium is as pronounced # as in full-grown sheep and goats. Though the deflection 

 of the face on the cranium may facilitate sucking, it is extremely probable that it was 

 originally acquired to facilitate grazing. During the first year, but more especially 

 during the first four or five months, grazing is difficult, because while the legs are very 

 long the neck is still extremely short. Even with the fore-legs wide apart it would be 

 difficult for a foal to seize short grass with the face in a line with the cranium. That 

 a face bent downwards as in sheep counts for something in the foal is suggested by the 

 fact that the deflection is more marked in foals of mountain and moorland ponies than 

 in foals of thoroughbreds — a race which has long lived under very artificial conditions. 



From the fact that the face is bent downward at birth it might be assumed that 



* The skull of a very young Giraffe is figured in Professor Lankester's paper on the Okapi (Trans. Zool. Soc, 

 vol. xvi.). In the young Giraffe it certainly looks as if the cranium had heen bent downwards on the face in the 

 interest of the horns. 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART III. (NO. 20). 79 



