BY C. W. DE VIS, M.A. V 



parallel with the horizontal, in Zygomaturus bends distinctly 

 outwards behind the base of the coronoid process. The extent 

 of this outbending will be best estimated from comparative 

 measurements ; though the Zygomaturus mandible is the 

 narrower along a line joining the outer surface of the bases of 

 the coronoid process in the ratio 195 : 203, at the back of the 

 ascending process it is wider in the ratio 255 : 235. While the 

 mandible contracts anteriorly, the expansion of the alveolar axes 

 remains greater than in Nototherium, the space between the 

 hinder molars being 116 mm., whereas to be in the same 

 proportion to the length of the molar series as in the Nototherium 

 it should be but 110 mm. 



The teeth of this series are notably smaller than in any 

 example of Nototherium, their combined length is but 144-5 mm. 

 In the Nototherium mandible under comparison, which 

 happens to have the shortest molar series I can find, its length 

 is 166 ; in other jaws, including Owen's examples, the length 

 goes on increasing to 186-9. Individual teeth are smaller in 

 just proportion — the last molar being 88 x 25 against 42-5 x 31, 

 The premolar is exactly the size of the milk tooth of Notothe- 

 rium figured by Owen.* 



The molars offer in their form and structure no significant 

 peculiarity — they maintain the close family likeness seen in the 

 molars of the allied genera Diprotodon, Nototherium, and Euo- 

 wenia, which led to the confusion between the two genera in 

 question, and still makes these teeth a most unsafe means of 

 identification. 



The incisors, on the other hand, afford differentiating 

 characters of value — they have to a less extent the curve and 

 the vertically extended, compressed, and rapidly tapering fang of 

 the incisors of Euowenia, and, as in that genus, their crowns are 

 much narrower, and more divergent at the apex than in Noto- 

 therium. A section of the fang on a level with the front of the 

 premolar is in form an oval 38-5 x 22 mm. ; the wall of bone 

 between these voluminous fangs is reduced to a thickness of 4 

 mm. — the narrower and more columnar fangs of Nototherium leave 



* Extinct Mam. Aust., Plate 40. 



