182 



surface of the crown : some parts of the margin of the dentine pre- 

 sent the curvilinear decussating lines which characterize the ivory of the 

 tusk. 



From the tertiary deposits of Ohio. Purchased. 



Tusks. 



742. The hasal conical lamellae of the tusk of a proboscidian Pachyderm, pro- 



bably the Mastodon giga?iteus : the largest circumference of this fragment 

 is sixteen inches, and its contour is slightly elliptical. 



From the tertiary formations of Kentucky, North America. 



Purchased. 



743. The basal part of the tusk of a young or female Mastodon giganteus. 



From the tertiary formations of Kentucky. Purchased, 



744. The central conical lamella? of the middle part of the same tusk : the 



fractured surface at the base of the cone demonstrates very strongly the 

 decussating engine-turned character of true ivory. 



From the tertiary formations of Kentucky. Purchased. 



745. The tusk of a young or female Mastodon giganteus : it is three feet six 



inches in length and one foot in basal circumference. 



The tusks of the Mastodon differ from those of the Mammoth in 

 the smaller amount of their curvature, which is also much more nearlv 

 on the same plane : the direction of the tusks is forwards, upwards and a 

 little outwards. 



From the tertiary deposits of Missouri. Purchased. 



746. A portion of the tusk of the Mastodon giganteus : the extremity has been 



unequally worn and polished ; the thin exterior coat of cement remains 

 at the opposite side of the extremity : the decussating curvilinear im- 

 pressions are very strongly marked at the broken ends of the fragment. 

 From the tertiary formations of Ohio. Purchased. 



747. A portion of the tusk of a proboscidian Pachyderm, probably the 



Mastodon giganteus : one-half has been worn away lengthwise, leaving 

 an imperfectly polished surface ; the outer coating of the tusk has been 



