CONTRIBUTION TO THE MORPHOLOGY OF THE MAMMOTH. 327 



indicated by an x in fig. 2), and this indentation on the surface of 

 the tnsk fitted to the cut surface of the penetrated wall of the alveo- 

 lus, the tusk was inserted as deep as it possibly could be. It then 

 fitted in its alveolus like a dagger in its sheath, and even the smallest 

 turning to the right or the left was impossible. 



The two tusks, which stand with their bases at an acute angle with 

 each other, after passing out of the alveoli first point downward, 

 then curve outward and somewhat upward, and finally the ends turn 

 inward. The worn surface (marked w4th an a in fig. 2) is found on 

 the upper side of the tip, sloping both outward and inward. Tusks 

 in an incomplete condition as regards development, such as those of 

 the immature Beresovka Mammoth, which have as yet no pronounced 

 spiral form, almost always have the worn surface on the upper side 

 of the tips. Exceptions correspond with the greater or less degree of 

 curvature, in which regard the tusks of Elepkas primigenius offer 

 numerous variations. Why the mechanical abrasion of the tusks in 

 the stage of development represented in the Beresovka Mammoth are 

 necessarily on the upper side of the tips I shall endeavor to exj^lain 

 later. 



It follows from the position of the tusks of the immature Bere- 

 sovka Mammoth that the points in this stage of development are 

 normally bent inward (fig. 2)." 



The spiral development of the tusks, which like all rootless teeth 

 grow steadily from the base until they reach complete development, 

 on account of the fact that the tips are first directed inward, leads 

 finally to their curving dowuAvard. Such strongly developed tusks, 

 with a curvilinear length of over 4 meters, are borne by the mam- 

 moth in my restoration. The distance between the tips reaches 

 about 50 cm. 



This position of fully-developed tusks makes at first, perhaps, a 

 strange impression. The tusks of the Beresovka Mammoth already 

 show some indications of the further development Avhich occurs in 

 Elephas primlgenius through spiral twisting, but we have tangible 

 proof of that development in various other tusks which are in a per- 

 fect state of preservation. 



The tusks in my restoration are in exact reproduction of the two 

 powerful specimens in the collection of the St. Petersburg Zoological 

 Museum. They are both in perfect condition and show both the pulp 

 and the tip intact. They illustrate in a typical manner the extraor- 

 dinarily strong spiral curvature of fully-developed mammoth tusks, 

 as their length from the base in a straight line is scarcely more than 

 half their length along the curves. H. Pohlig describes these two 



a See W. Salenski's work on the mamuioth (in Russian), St. Petei'sburg, 1903. 

 p. 84, pis. 24, 25. 



