1068 ON A SUPPOSED NEW SPECIES OF NOTOTHERIUM, 



the entries of the mid-valley. The anterior and posterior talons 

 are broader than the lateral ridges and commence at the inner 

 angle of each tooth. The teeth m'' and m- are of full size, recently 

 brought into mutual contact; their length individually and serially 

 is not diminished by compression. The summits of the lobes of 

 m^ are touched by wear, but their dentine is not exposed. The 

 lobes of d^ are more than half worn down, and this tooth was 

 evidently in use, as it is in N. mitchelli, before the eruption of the 

 premolar. 



Length from tip of incisor to entry of dental canal... 346 mm. 



Length of molar series ... ... ... ... 175 mm. 



Length of diastema ... ... ... ... ... 70 mm. 



External height to basal ridge of nr ... ... 83 mm. 



Length of incisor from outlet ... ... ... 70mm. 



Length of p'^ . . ... ... ... ... ... 17 mm. 



Breadth of p' ... ... ... ... ...14-5mm. 



Length of m''... ... ... ... ... ... 46 mm. 



Breadth of nr"* ... ... ... ... ... 29-5 mm. 



The changes which may take place in the jaw of the present 

 species during the progress of adult life may be instructively 

 observed in the example, clearly identified by the premolar, to 

 which allusion has already been made. This fine relic, No. 5451, 

 is a rather aged mandible, wanting the incisive region, coronoid 

 plates, alar expansions, and condyles. The more obvious changes 

 are the increased depth, to the amount of one-sixth, with corres- 

 ponding thickening of the horizontal ramus and the accentuation 

 of the specific character afforded by the position of the inlet of the 

 dental canal which has now receded from the postmolar angle to 

 a distance equal to the length of m"*, and has had its aspect turned 

 dorsad by an extension behind it of the ridge which in earlier life 

 it terminated ; this ridge now rises to join a convex surface 

 below the condylar process ; the outer mandibular wall is much 

 flatter, the convexity passing into the root of the coronoid process 

 commencing rather suddenly beneath m' and inferiorly subsiding 

 before reaching the lower edge of the jaw. The coronoid process 

 is now opposite the hinder lobe of m^. The postmolar platform 



