and of other Animals, found on the left Bank of the Irawadi. 373 



and disappearing ; and behind it^ we liave the cavity in which the young tooth 

 which was intended as a successor to that in existence^ must have been in the 

 course of formation *. 



The denticules of the tooth are much more compressed than those in the 

 species last described ; they are closer together f , and the enamel appears to 

 be not so thick. Tiiey form a series of plates mucronated with small points. 

 There is no apparent commissure, neither is there any central depression : 

 on the contrary, the plates rather rise in the middle. 



This tooth approaches still more nearly to that of the elephant, and the 

 contour of the jaw is in unison with the appearance of the tooth. Perhaps we 

 should not be far from the truth, if we were to conclude that the species to 

 which this tooth belonged, formed the passage from the Mastodon to the Ele- 

 phant. It is not impossible, however, that there may yet be a link wanting, 

 which might be supplied by an animal having a tooth composed of a greater 

 number of denticules, increasing in depth, and having the rudiments of crusta 

 petrosa, — that necessary ingredient in the tooth of the elephant, — (for it is 

 the animal mortar, as it were, by which the plates or denticules are cemented 

 together) — the entire absence of which, distinguishes the tooth of the mas- 

 todon. 



The habits of this species must have been nearly allied to those of the last. 

 — But we must now leave this more interesting part of o.ur subject, to consider 

 the more common forms of the order now before us. 



In this group we have remains of the genera Hippopotamus, Sus, Rhino- 

 ceros, and Tapir. 



Hippopotamus. — Of this genus there are but few fragments, nor are they 

 sufficiently characteristic to enable us to pronounce on the species, though 

 there is no doubt as to the genus. The animal to which these remains be- 

 longed, must have been smaller than the recent species ;|;. 



Sus. — Of this genus there is only a single specimen, consisting of a small 

 portion of the lower jaw, containing one molar tooth and the fragment of 

 another. This species could not have been large §. 



Rhinoceros. — Of this genus, we have, among other remains, a small por- 

 tion of the upper jaw, containing two molar teeth ; the remnant of the jaw is 

 only just sufficient to hold the teeth together. There is likewise a single 



* See Plate XXXVIII. fig. 2. 



f Eight denticules of M. elepbantoides occupy the same space as five denticules of M. latidens. 



t See Plate XL. fig. 3. 4 ; and Plate XLI. fig. 19. 20. § See Plate XL. fig. 5. 



