150 



It will be observed that, in the Thylacine — the most carnivorous of modern Marsu- 

 pials — the depth of the notch between the condyle (b) and coronoid (c), or what Dr. Fal- 

 CONBE indicates by the term "pedunculate," is relatively greater than in Sarcophilus. 

 The two recede in this respect progressively further from the Koala and the Aye-aye. 

 If Plagiaulax had shown less degree of " pedunculation " and a higher position of the 

 condyle than in Thylacinus or Sarcophilus, and had, in these respects, approached nearer 

 to Ghiromys or Phascolarctos in mandibular modifications, an inference of corresponding 

 approximation in diet, or herbivorous application of jaw, would have been legitimate. 

 1 claim the same quality for my conclusion, that as the carnivorous characters of the 

 lower jaw are maximized in Plagiaulax (fig. 10) with strong indications of the same 

 structure in Thylacoleo (fig. 8), so the carnivority of both genera is the more plainly 

 demonstrated. 



It is not, however, a solitary character, but an association of characters, which esta- 

 blishes this conclusion. In Sarcophilus the inner wall of the ramus above the sym- 

 physis, as in Thylacoleo, is broad, nearly horizontal, gaining breadth as it recedes and 

 extending back to the third premolar. The symphysis is more extensive, and unites 

 together more firmly the rami of the jaw in Sarcophilus and Thylacinus than in Poephaga. 

 In the Kangaroos it permits the scissor-blade movements of the horizontally flattened 

 procumbent incisors. In Bettongia the symphysis does not reach backward to the socket 

 of the single premolar. Thylacoleo and Plagiaulax resemble the existing marsupial 

 ( 'arnivora in the extent of the mandibular symphysis, and in the firmness of the union 

 of the parts so joined together. 



Position of condyle relates to the force with which the mandible is worked, shape and 

 pedunculation of the condyle to the direction of the working force. 



The flattened or less convex articular surface favours the rotatory movements; the 

 more convex, especially transversely extended and pedunculate or subpedunculate, condyle 

 indicates the ginglymoid articulation with greater extent of divarication or wider gape, 

 and more habitual movements of the jaw in one plane, or limited more or less thereto. 

 The rotatory grinding movements of the mandible are commonly associated with a high 

 position of the condyle and vegetable diet ; the vertical biting movements are commonly 

 associated with a low position of the condyle and animal diet. But the advantage of a 

 long lever afforded by a lofty coronoid process (figs. 10, 11, 12, c) and low-placed condyle 

 (ib. b) may correlate with powerful biting and gnawing actions, as in the working of the 

 maximized scalpriform teeth of Chiromys (fig. 9, i). 



Here, however, the coronoid (c) is comparatively low : the condyle (ib. b) is narrow ; 

 its convex curve is chiefly longitudinal, or from above downward ; there is no constriction 

 or neck ; the supporting part of the articular surface is continued directly upward and 

 forward to the coronoid (c), and almost as directly downward and forward to the angle (a)*. 

 In similarly placed condyles for biting, piercing, lacerating, and killing actions of the 



* Owen, ' Monograph on the Aye-aye,' 4to, 1863, p. 20. pi. 8. figs. 7, 9 (also ' Transactions of the Zoological 

 Society,' vol. v. pt. 2. pi. 20. figs. 7, 9). 



