20 THE PKJEVALSKY HOESE. 



words on craniological measurements in general. These already 

 play an important part in the systematic classification of mammals, 

 although the inethods employed have only recently been elaborated. 

 Consequent upon the recent nature of the application of cranio- 

 metry to mammals in general, different authors choose different 

 bones and different points of the skull from which to make their 

 measurements, with the result that there are divergences in the 

 results of researches not only in skulls of different genera and 

 species, but also in those of the same species. Some authorities 

 make the mistake of giving too many measurements : others give 

 too few. The former furnish unnecessary material which mars the 

 clearness of the conclusions ; while the incompleteness of the 

 measurements of others comes into i^rominence when their re- 

 searches are employed for the purpose of determining if a given 

 skull belongs to this or that species. 



The object of the study of the skull and of craniological measure- 

 ments should be the discovery of essential and specific cliaracter- 

 istics by which a given skull may be distinguished from the skulls 

 of closely allied genera and species. In many mammals, rodents 

 for instance, not only does the relative size of certain parts of 

 the skull serve as a specific character, but so also does the absolute 

 size. Although the horse does not come into this category, never- 

 theless the absolute figures of the skull measurements can be 

 used advantageously, to a certain extent, for purposes of deter- 

 mination, as was demonstrated by the measurements made by 

 Franck,* Nehring and Czerski, and by the tables drawn up by 

 myself. 



Great credit is due to Nehring as being the first to devise a 

 rational method of craniometry by which the characteristic con- 

 figuration of a skull could be demonstrated. To the measurements 

 used by Nehring, Czerski added others ; with the result that the 

 number now employed is considerable. Nehring's most important 

 measurements were for the purpose of indicating the width, length 

 and height of the skull and the mandible. The width of the skull 

 he took at three points : (1) the distance between the posterior 

 margins of the orbital cavities — Frontal width ; (2) the distance 

 between the zygomatic ridges of the superior maxillary bones — • 

 Facial 11'idth ; and {?>) the transverse distance between the most 

 prominent parts of the nasal region — IVasal width. Of these, 

 Nehring considered the frontal width to be the most important, 

 and compared it with the length of the base of the entire skull 

 (Basilar length), and with the length of the upper surface of the 



* Franck. Ein Beitrag zur Eassenkunde unserer Pferde. Landwirtksck. 

 Jahrbiicher, IV., 1875. 



