1836.] Mastodon Angustidens. 295 



ed, and gradually unite, until the mamillse are worn away entirely, 



when the tooth is left with merely a surface of ivory surrounded by 



enamel. 



The drawings are intended to represent the tooth at these different 



stages ; from the state of germ, to the old and worn down tooth, 



shewing the intermediate state of detrition at different ages. 



PI. xi. Fig. 1 . Fragment of tooth in germ, with the enamel on one 

 of the mamillae fractured. 



Fig. 2. A very perfect molar of a young but adult animal, the front 

 surface being moderately worn, and the rear portion in the state of 

 germ. This is the right molar of the lower jaw. The length of 

 this tooth is 9'2 inches or '234 metres, and the bi'eadth measured 

 on the base or lower bulge of the mamillse 2*95 inches or "074 

 metres ; it consists of six pair of points or mamillse, with apparently 

 (as the fossil is slightly fractured at this point) a bilobed talon in 

 the rear. The coronal surface is here shewn. 



Fig. 3. An internal view of the same tooth. 



Fig. 4. An external view of the same, exhibiting the obliquity of 

 wear on the coronal surface. 



Fig. 5 and 6. Fragment of a tooth of a greater age than the preceding. 



Fig. 7 and 8. Fragment of tooth with jaw attached ; this is a portion 

 of the left molar of the lower jaw of an animal of the same age as 

 that represented in figs. 5 and 6, distinctly shewing the cup-like 

 cavities formed by the detrition and gradual junction of the ma- 

 millse : the obliquity of wear towards the outer surface is here very 

 distinctly marked. 



Fig. 9 and 10. Fragment of a tooth of the same age as the pre- 

 ceding. 

 The three last specimens have belonged to animals of nearly the 



same age ; the mamillee are much worn, and we see the gradual oblite- 

 ration of their independent hollows, reducing the coronal surface to 



the appearance exhibited in figs. 11 and 12. 



Fig. 11. Shews the detrition at an intermediate state between figs. 9 

 and 10, and fig. 12. The posterior portion of this specimen still 

 retains the encircling lines of enamel on the worn down points, 

 whilst the portion in front has arrived at its last stage of wear. 



Fig. 12. May be considered as a representation of the tooth in its 

 final state of detrition, when all marks of the mamillated form of 

 crown is obliterated, and nothing remains but an outer border of 

 enamel encircling a deep internal hollow of ivory. 

 I wish to draw attention particularly to the alternating position of 



the mamillse, which I consider to be the chief specific character, and 



which is distinctly marked throughout the whole series ; and, referring 



