94 rOSSIL MAMMALIA OF THE 



of the outer crotapliyte depression, and from the concomitant extent of the fractured base 

 of the coronoid process in the least mutilated mandible of Thylacoleo, which has yet reached 

 me (fig. 15), I infer a breadth and general development of the coronoid process, and a 

 position of the condyle corresponding, more or less, with those characteristic of Flagiaulax, 

 SarcopJdlus, and Thylacynus. 



The dentition of the upper as well as of the lower jaw of Thylacoleo being ascertained, 

 its formula gives : — 



. 2—2 1—1 4—4 1—1 _ .^o 

 ^ lUl' ^ 0=0'^^ 3—3' ^'^ 2-2' ~ ^• 



Thus, so far as the dentition of Playiaulax is known, it more closely resembles that 

 of TJiylacoleo than of any other Marsupial. 



From the characteristic reduction in size and number of the molar teeth, I have 

 associated them as members of a ' paucidentate ' family or Section of Diprotodonts. 



In this section may be discerned an interesting illustration of the Law or Tendency 

 from the General to the Particular as species approach the present time in geological 

 position. 



The extinct pouched Carnivore of the Neozoic period has the functional or carnassial 

 premolars reduced to a single tooth on each side of the lower jaw ; the extinct pouched 

 Carnivore of the Mesozoic period retained, in one species, three premolars of the carnassial 

 type, in another species four — the normal number — on each side of the lower jaw. 



The parallel runs very close with that which the placental Carnivora show within the 

 limits of Tertiary time; as when, e.y., we compare the Miocene Hycenodon and its three 

 lower camassials with the modern Hyana, where they are reduced to one ; or when we 

 compare the Miocene Amphycyon with its three upper tuberculars with the modern Vrsus, 

 where they are reduced to two. 



The alleged ' well-ascertained ' conclusion as to the herbivorous nature of Playiaulax 

 allowed only the contrast with the rich and well-adapted series of grinding teeth in the 

 Poephaya and placental Herbivores to be thought of, and blinded the Objector to the 

 suggestive instance of ancient adhesion to type^ which the carnassials of Playiaulax, 

 viewed as a Carnivore, force upon the attention. 



Because certain saltatory vegetable-feeding Marsupials have one trenchant and vertically 

 ridged mandibular premolar, occupying a small proportion of the entire molary series, it is 

 not admissible that three or four trenchant and obliquely ridged mandibular premolars, 

 forming a large proportion of the entire molary series, afford adequate grounds for con- 

 cluding the limbs to be ' macropodal,' and the beast to be herbivorous and a " Marsupial 

 form of Rodent." ' 



A life's experience in the labour of restoring, from fragmentary evidences, an extinct 



^ Falconer, ' Quarterly Journal of the Geol. See.,' vol. xiii, p. 276 ; also, ' Palseontographical Memoirs, 

 &c.,' vol. ii, pp. 421, 427. 



~ lb., ib., vol. xviii, p. 349, and 'Pal. Mem.,' vol. ii, p. 425. 



