214 Dr. N. Severtzoft' on tJie Ma mm ah of TurTcestan. 



From these Tables it will be noticed that the cross measure- 

 ments of the skull, taken separately, show the specific distinc- 

 tions only in adult specimens ; and even then they are not 

 imjiortant or considerable, except the sharp projections of the 

 lachrymals of the adult Oris PoUi. But the proportions (or 

 the measurements stated in decimal numbers) are constant in 

 all ages, although they are not so distinct in young animals as 

 they are in adult. 



As regards the different species, 0. Ileinsii by the general 

 shape of the skull is nearer to 0. Polii of equal age than to 

 0. Karelim', and differs from the former very little ; but, as 

 already stated, the shape of the different parts of the skull 

 separately and the spiral of the horns of 0. Ileinsii and 

 0. Polii furnish the most striking differences. 



The alteration of the skull according to the age depends 

 principally upon the development of the horns ; and conse- 

 quently the decimal numbers of the measurements in the dif- 

 ferent ages of one species do not alter so considerably as their 

 measurements in inches do. As all the measurements of the 

 skull alter according to the animal's age, the diameters of the 

 skull even diminish in their proportion to the length of same, 

 as the frontal grows rather more quickly than any other parts. 



The changes of the different parts of the skull according 

 to the different ages are most numerous in 0. Polii] and I 

 will just mention how useful these changes are in deter- 

 mining the age of the animal by means of the gradual deve- 

 lopment of its horns and the different parts of its skull. The 

 former are the more ti-ustworthy, because in growing the 

 horns do not lose their annulations, but retain them, sharing 

 their gradual development. The horns are separated from the 

 skull by an annulation, Avhich does not disappear but is 

 gradually pushed forward by the one that is growing next to 

 it ; and this is the way in which the sulcations are formed, 

 which are deepest on the frontal sm-face of the horn. 



The growth of the horns is not equally quick at all seasons 

 of the year ; in winter they grow more slowly and weakly, 

 whilst in spring witli the fresh food they again grow very fast 

 and strong. In spring the annulation at the base of the horns 

 grows more quickly than it is able to elevate the one before it ; 

 and consequently the space between them forms a sharp 

 impression round the horn. These impressions indicate the 

 annual increase of the bonis, and enable one to count by them 

 the number of years the animal has lived. There are, however, 

 some circumstances which render the reckoning liable to en-or ; 

 and these are the following : — 



1st. The annulations of the horns are not always sepa- 



