618 UNGULATES. 



The last, or third true molar, (ib. fig. 10 & 11, m 3) is subject 

 to some variety of configuration, as well as size ; it supports four 

 bifid transverse eminences and a posterior talon ;(1) but this is 

 often developed into a fifth bifid transverse eminence, smaller than 

 the others, and is sometimes followed by a sixth tuberculate lobe 

 or talon. The antero-posterior diameter of the crown ranges from 

 seven and a half inches to eight and a half inches, its transverse 

 diameter at its thickest (anterior) part, from four inches to four 

 and a half inches. The remains of the lateral basal ridges are 

 usually present in this and the two preceding molars as tubercles 

 at the outer and inner ends of the transverse valleys. The first 

 and second transverse ridges are usually supported by a single 

 root, the rest of the molar by a large conical mass subdivided 

 into four or more roots. 



The successive molars have here been described as they appear 

 in the lower jaw ; those above scarcely difi'er save in a slight increase 

 of transverse diameter and more subdivided roots. 



The superior tusks of Mastodon giganteus project more forwards 

 than in the Elephant, and are slightly curved upwards and outwards. 

 The length of the exserted part of those in the skeleton of the 

 adult male Mastodon in the British Museum surpasses seven feet, 

 along the curve. Some smaller and straighter specimens, which, 

 from the contraction of their open basal end, would seem to have 

 belonged to aged individuals, indicate a sexual inferiority in the 

 length of the upper tusks in the female of this species. 



The inferior persistent tusk in the lower jaw is commonly 

 about three inches in diameter and one foot in length ; it is nearly 

 straight. Cuvier has apparently figured the end of one of these 

 tusks in the first Edition of the ' Ossemens Fossiles, Grand Mas- 

 todonte' PI. 3, fig. 4 & 5. In the same plate he has well repre- 

 sented a lower jaw of an old male Mastodon showing the persistent 

 alveolus of the single tusk, in fig. 2. The original of this figure 



(1) This variety is figured by Dr- Hays in the lower jaw of an old female Mastodon, loc. 

 cit. PI. 23, & PI. 24, and in that of an old male Mastodon, with one tusk, in PJ. 29. Also by 

 Cuvier, loc. cit. ' Grand Mastodonte,' PI. i, figs. 3 & 4. 



(2) This variety is figured by Dr. Hays, loc. cit. PI. 21, f, and by Cuvier, loc. cit. fig. 2. 



