TEETH OF DIPHYODONTS. 



237 



Marsupials approximates to the insectivorous type, and leads 

 thereto from the flesh-feeding;; o-enera. 



o o 



Myrmecobius is characterised by the following remarkable 

 dental formula: 



.4.4 1.1 



3.3 



6.6 



Dentition of Myrmecobius. 



The number of true and false molars, eighteen in both jaws, 



exceeds that of any other known existing Marsupial. The molars 



are multicuspid, and both the 224 



true and false ones possess 



two separate fangs. The iru- 



ferior molars are directed 



obliquely inward, and the 



whole dental series describes 



a slight sigmoid curve, fig. 



225. The premolars present 



the usual compressed trian- 



gular form, with the apex slightly recurved, and the base 



more or less obscurely notched before and behind. The canines 



are very little longer than the false molars. The incisors are 



minute, slightly compressed, and pointed ; they are separated 



from each other and the canines by wide intervals. 



The extinct genus Amphiiherium is founded on fossil remains 

 of lower jaws and teeth discovered in the oolitic slate at Stones- 

 field, in Oxfordshire, and it receives elucidation from the dental 

 characters of the previous genus, but is remarkable for 225 

 having a still greater number of molar teeth. The 

 dental formula is as follows : 



?.? 



j L ". f 

 3.3' C 



j| 



6.6' 6.6" 



There being thus thirty-two teeth in the lower jaw, 

 and probably as many in the upper jaw. 



The following dental fornmla- 



.5.5 1.1 

 i r 



3.3' 1.1 



3.3 



4.4 



1 Q 



7TTT' " , 7 * 



characterises a number of Marsupials commonly known 

 in Australia by the name of Bandicoots, fig. 226. The 

 teeth which offer the greatest range of variation in the 

 present genus (Perameles} are the external or posterior 



teetli Myrme- 



incisors and the canines : the molars, also, which ori- COMUS. 

 ginally are quinque-cuspidate, have their points worn away, and 

 present a smooth and oblique grinding surface in some species 

 (fig. 222, m, vol. ii.) sooner than in others. 



