Dr. N. SevertzofF o;i the Mampials of Turkestan. 215 



rated by these furrows with uniform distinctness. Frequently, 

 from want of food or from illness, narrow annulations are formed 

 round the horn besides those caused by the annual interruption 

 of their growth in winter, which they much resemble. 



2nd. In addition to these irregular annulations there are 

 other secondary annulations, separating those indicating the 

 annual increase of the liorns. The furrows formed by these 

 differ from those dependent on the annual increase of the horns 

 in their not being so deep and in their not extending all round 

 the horn. They are, when present, nearly always distinguishable. 



3rd. Finally, the rings formed whilst the animal is young 

 are not so distinct as those formed when it is adult, as 

 with advanced age the rings get thicker. These early 

 rings, in getting towards the end of the horn, sometimes get 

 rubbed off and the horn itself gets blunt with advanced 

 age ; this is the case in particular with 0. Polii, because of 

 the inner spiral of the horns getting wider towards the end of 

 the horn ; consequently only the minimum of the animal's age 

 can be fixed — for instance, that the animal is not younger 

 than ten or twelve years, but how much older is doubtful. 

 In specimens wliich are not above ten years old the age 

 can usually be correctly ascertained, although sometimes this 

 cannot be done without difficulty. Very little confidence can 

 be placed in the determination of an animal's age by the anky- 

 losis of the different bones of its skull, this latter being an 

 uninterrupted process. 



The proportions between the development of the horns and 

 the ankylosis of the skull-bones give also specific characteris- 

 tics wliich are in most cases constant, although some speci- 

 mens of one and the same species differ slightly in that 

 respect ; but this is more or less the case with all mammals. 



In examining the skulls of different species I find that the 

 bones of the skull of an 0. Polii about two and a half years 

 old are more firmly ankylosed than those of specimens of 

 0. Karelini and 0. Heinsii of about four and a half or five 

 years of age. The above specimens of 0. Polii and 0. Karelini 

 are complete, so that the age can be checked by the horns as 

 well as by the general size of the animal ; and this shows that 

 0. Polii has not nearly reached its full size, whilst 0. Karelini 

 has fully done so ; but notwithstanding this, from the exami- 

 nation of the skull alone, the latter would have appeared to 

 be the youngest. 



It cannot be admitted that 0. Karelini and 0. Heinsii 

 grow twice as quickly as 0. Polii^ and that at the same time 

 the bones of their skulls ankylose more slowly : the one seems 

 to disprove the other. It is more likely that the parts of 



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