1902.] ADAPTATIONS IX DIPROTODOXT MARSUPIALS. 31 



this muscular action. It is thus possible that the movement of 

 the mandible towards one side is effected by the combined action 

 of a part of the masseter of the opposite side, and in less degree 

 by the pterygoideus inter7ius of the same side. When the man- 

 dible has come to the desired lateral position so that the outer 

 margin of its molars comes quite opposite that of the corresponding- 

 molars of the maxillary, both viasseters and •pterygoidei contract 

 and press the jaws together. The lower jaw then glides back 

 into the normal position, owing to the direction of the sloping- 

 surfaces of the molar crowns as described above. 



In the true Phalangerids the mandibular condyle Avhich serves as 

 the pivot in the above-mentioned lateral rotation of the lower jaw 

 is steadied behind by the very solid post-glenoidal bone. In the 

 Wombat the condyle is only steadied on the inner side. We may 

 conclude from this that the chewing of this animal takes place 

 in a different manner from that in the true Phalangerids. The 

 sloping of the molar surfaces is also quite different in the Wombat, 

 i. e. inwards in the lower and outwards in the upper jaw. In 

 addition to this they are concave with sharp enamel ridges all 

 round, but especially protruding at the inner and outer margins. 

 It seems as if the chewing were effected by alternating trans- 

 verse movements of the lower jaw, and that the triturating action 

 on each side chiefly takes place when that side of the mandible is 

 moved in a median direction. As my material is not sufficient, 

 however, I shall not make any detailed statements. 



Tarsipes takes, with regard to its dentition, the same extreme 

 position as it does with regard to the development of its intestine. 

 The mandibvilar incisors are slender and form together a point, 

 which perhaps might be used in making holes in the corolla of 

 flowers rich in honey for the insertion of the tongue. Together 

 with the upper incisors and canines they may also act as a pair 

 of pincers, useful when the animal catches small insects as it is 

 reported to do \ But the well-known rudimentary condition of 

 its molar series — in the specimen before me 2/2 to the left, 3/3 

 to the right — as well as the weakness of the lower jaw, without a 

 2)rocessus coronoidetts and angular inflection, make chewing or 

 even crushing of any hard prey impossible. 



Thus the development and structure of the dentition, as well 

 as of the intestine, show a beautiful correspondence with the 

 diet and habits of the animals in the whole family Phalangeridfe 

 the more striking through the polymorphism witlain so restricted 

 limits as those of such a natural group. 



1 Conf. Lyciekker's ' Handbook,' p. 121 (quoted on p. 13). 



