47 
1906-7.] Observations on the Skull of Equus prjevalskii. 
ment of considerable value, because it lies between points which are super- 
ficial in the living animal. By comparing it with the length of the 
cranium, taken as 100, the cephalic index A of the subjoined table was 
computed. The condylar breadth, however, is not the breadth of the actual 
cranial box in the horse ; nor was it altogether easy to determine upon a 
measurement which would accurately define the width of the cranium. 
Finally, however, a maximum parietal breadth between points on the 
parieto-squamosal suture was decided upon ; and this was compared with 
the length of the cranium ( = 100) in a cephalic index B. 
TABLE I. 
Cranium. 
E. prjevalskii. 
Celtic. 
Iceland. 
Length, 
170 
171 
184 
Condylar breadth, 
Maximum parietal breadth, . . 
188 
178 
189 
87 
90 
93 
Cephalic index A, . 
110-58 
104-09 
102-71 
Cephalic index B, . 
51-17 
52-63 
50-54 
From the above indices it is clear that the Prjevalsky cranium was 
much wider on a level with the temporo-mandibular articulation than either 
the Celtic or Iceland cranium (cephalic index A). The Iceland cranium 
was the narrowest ; and the Celtic intermediate, but much nearer the 
Iceland than the Prjevalsky. Cephalic index B also demonstrates the 
relative narrowness of the Iceland cranium. It is of interest to note that, 
according to index B, the Prjevalsky cranium was slightly narrower, as 
compared with its length, than the Celtic, in spite of the fact that the 
width of the Prjevalsky skull measured between the temporo-mandibular 
articulations was much greater than that of the Celtic horse. 
The measurements of the facial parts of the three skulls brought out 
certain distinctive features in a very definite manner, and corroborated 
conclusions which could be drawn from a mere inspection. The length of 
the face was measured from the inter-orbital point to the alveolar point, and 
its breadth between the most distant points on the sutures separating the 
malar and maxillary bones. A facial index was computed by comparing 
the breadth with the length taken as 100. In the living animal the width 
of the face, as determined by inspection, depends upon the transverse 
diameter between the two orbits. For this reason, it was decided to include 
a frontal width in the facial measurements, by determining the maximum 
distance between the post-orbital processes of the two frontal bones. A 
frontal index was then calculated in the same manner as the facial index. 
