48 
Proceedings of the Royal Society of Edinburgh. [Sess. 
A comparison of the figures in the following table with those in Table I. 
shows that the frontal breadth gives the greatest transverse measurement 
of the whole skull ; or, in other words, that the skull of the horse is widest 
on a level with the orbits. At the same time it will be seen that the 
Prjevalsky skull differed from the other two in that the frontal breadth 
exceeded the condylar breadth by only 0*5 mm. : a point of some moment 
as demonstrating a peculiarity of the head behind the orbit. 
TABLE II. 
Face. 
E. prjevalskii. 
Celtic. 
Iceland. 
Length, ...... 
370 
333 
336 
Breadth, ...... 
166 
159 
177 
Facial index , ..... 
44-86 
f7-74 
52-67 
Frontal breadth, ..... 
188*5 
192 
206 
Frontal index , 
50-94- 
57-65 
61-30 
Cranio-facial length, .... 
493 
467 
485 
Cranio-facial index , .... 
75-05 
71-30 
69-27 
That the Iceland skull had a short, broad face is shown by the facial 
and frontal indices, as well as by the absolute measurements. The 
Prjevalsky horse, on the other hand, had a long, narrow face; the Celtic 
skull occupying an intermediate position. 
In addition to determining the relationship between the length and 
breadth of the face, the proportion which the face formed of the length of 
the entire skull was also ascertained. This was done by measuring the 
distance from the opisthion to the alveolar point — cranio-facial length — 
and computing an index as follows : — 
r . . . - 7 .7 Length of face x 1 00 
Cranio-facial length 
In this way it was shown that the face of Equus prjevalskii was long in 
relation to the skull as a whole ; that the Iceland horse had a short face ; 
and that the Celtic horse stood between the two. 
It might have been expected that the palate in the three horses would 
vary with the face. This, however, was not quite the case. The length- 
breadth or palatine index was certainly highest in the skull of the Iceland 
type, thus indicating a relatively broad palate in conformity with the broad 
face ; but in the wild and Celtic horses the palatine indices are practically 
identical, in spite of the fact that the wild horse had relatively the longer 
face. The actual measurements are as follows : — 
