46 
Proceedings of the Royal Society of Edinburgh. [Sess. 
VIII— Craniometrical Observations on the Skull of Equus 
prjevalskii and other Horses. By O. Charnock Bradley, 
M.B., D.Sc., F.R.S.E. 
(Read November 19, 1906. MS. received March 18, 1907.) 
The peculiarities of the skull of the Prjevalsky horse {Equus prjevalskii) 
have been extensively studied by Salensky of St Petersburg, and compared 
by him with the skulls of various other members of the genus Equus. No 
special attempt, however, has been made to contrast the skull of the wild 
horse with that of different varieties of the domestic horse. There can be 
little doubt that given as rich a collection of Prjevalsky horse skulls as 
were at the disposal of Salensky, and given, at the same time, a represent- 
ative collection of skulls of different types of the domestic horse, many 
points of great scientific interest would emerge from a comparison. In 
default of such a wealth of material, it is clearly desirable that opportunities 
afforded by even isolated specimens should be turned to as good an account 
as possible. In this conviction, Professor Cossar Ewart recently asked me to 
make measurements of the skull of a Prjevalsky horse, about three and a 
half years old, and compare them with similar measurements of the skulls 
of horses of the Celtic and Iceland or Forest types. The comparison proved 
of interest ; and though the material was certainly not sufficiently abundant 
to justify any dogmatic conclusions, the differences in the three skulls are 
so striking as to merit record. 
In the Prjevalsky horse the nasion was found to be placed relatively 
much farther forward than in the other skulls. This being so, it was 
decided to abandon this point as indicating the craniometric line of demar- 
cation of cranium and face. On the suggestion of Professor Ewart, a line 
crossing the skull transversely on a level with the anterior border of the 
post- orbital process of the frontal bone was substituted, since the mesiahy 
sectioned skull showed that it fairly accurately indicated on the surface the 
level of the anterior limit of the actual cranial cavity. The mid-point of 
this transverse line may be referred to, for convenience, as the inter-orbital 
point. 
The length of the cranium was measured from the opisthion to the 
inter-orbital point ; and its breadth was estimated by two diameters. The 
transverse diameter of the cranium taken from the outermost part of the 
condyles on the squamous temporal bones {condylar breadth) is a measure- 
