Fossil Molar Tooth of the Mastodon Australis. 575 



The amount of difference between the Australian molar and those 

 of the European Mastodon angustidens, though small, equals that by 

 which the molars of the Mastodon Andium are distinguished from 

 the molars of the Mastodon angustidens ; and if species so nearly al- 

 lied have left their remains in countries so remote as France and 

 Peru, still more if the Mastodon angustidens or longirostris formerly 

 existed, as has been affirmed, in North America, we need feel the less 

 surprise at the discovery of a nearly allied species in the continent of 

 Australia. 



The fossil in question is the crown of an incompletely formed 

 molar, with the summits of its mastoid or udder-shaped eminences 

 entire, its fangs undeveloped, and its base widely excavated by the 

 unclosed pulp-cavity. It supports six principal mastoid eminences 

 in three transverse pairs, with a narrow ridge at the anterior part of 

 the base of the crown, and a small quadrituberculate talon or basal 

 prominence posteriorly : the three transverse eminences are joined 

 together by a pair of small tubercles at the basal half of each inter- 

 space, placed in the long axis of the crown, and rather to the outer 

 side of the middle line of the grinding surface, fig. 2. 



The length or antero- posterior diameter of the crown is four inches 

 ten lines : the breadth of the posterior pair of tubercles is two inches 

 eleven lines : the height of the middle eminences from the base of 

 the crown is two inches six lines : the tooth is apparently the fourth 

 molar of the left side of the lower jaw. In comparison with a corres- 

 ponding molar in the same state of growth of the Mastodon longiros- 

 tris* of Kaup, a cast of which is now before me, the Australian 

 molar differs in having the principal transverse eminences more com- 

 pressed antero -posteriorly in proportion to their height, and tapering 

 to sharper summits, which however are obtuse and bifid. The 

 breadth of the tooth slightly increases to the posterior pair of emi- 

 nences, whilst in the Mastodon longirostris and angustidens the crown 

 maintains the same breadth, or more commonly becomes narrower 

 from the anterior to the posterior pair of mastoid eminences. 



Other differences observable on a minute comparison are too tri- 

 vial to deserve notice, especially when observed in only a single ex- 



* If this species be distinct from the Mast, angustidens of Cuvicr, the molar teeth seem to 

 mo to offer precisely the same characters. 



