1862.] FALCONER PLAGIAULAX. 3o7 



trenchant *, and I have shown above that the tooth is essentially 

 alike in Plagiaulax. If, therefore, the function is to be deduced 

 with such facile certainty from the mere form, the premolar of 

 Hypsiprymnus ought also to be carnivorous. But we know that the 

 genus is so strictly herbivorous that the family to which it belongs 

 has been regarded as representing in the Marsupialia the Euminants 

 of the Placental Mammals. With this fact before us, is it likely 

 that the premolars of Plagiaulax were applied to cut and divide 

 flesh ? Does the serrated edge indicate a flesh-cutting function ? 

 The singular agreement between the two genera in their premolars, 

 down even to the number of grooves, however trivial and unim- 

 portant the character may appear to be, has, I confess, weighed 

 greatly with me in forming my opinion. No special function has, 

 as yet, been connected with the peculiarly grooved tooth of the living 

 Kangaroo-rat. The agreement is therefore purely empirical ; but as 

 the character, according to our present knowledge, is confined, among 

 many hundred genera of Mammalia, to certain species of Hypsi- 

 prymnm and to Plagiaulax, those who have faith in the constancy 

 of the manifestations of nature will not lightly believe that it was 

 common to these two genera alone without implying affinity ; and 

 when this is coupled with the obviously phytophagous type of the 

 incisors, the conviction will be confirmed. I need hardly add that I 

 regard the carnivorous deduction from the shape to be arbitrary and 

 untenable. 



[AYilliam Hunter, a century ago, by a parity of reasoning, arrived 

 at the conclusion that the Mastodon of North America, from the 

 trenchant form of the transverse crown-ridges of its molar teeth, was 

 an extinct, colossal, carnivorous animal, in short, a kind of predaceous 

 flesh-eating Elephant t. The error in his case, as in the correspond- 

 ing one of Leibnitz, was excusable, comparative anatomy having been 

 then in its infancy. But it is not a little startling to see the same 

 sort of unsound deduction reproduced, in regard of one of the most 

 pigmy of Mammals, half a century after Cuvier, by his luminous 

 demonstrations, had indicated the method by which such signal mis- 

 takes might be avoided in future. — Oct. 15th.] 



Professor Owen perceives another indication of resemblance be- 

 tween Thylacoleo and Plagiaulax in the proportions of the large 

 premolar to the succeeding molars. In both, there are but two 

 molars, and in so far the agreement is clear ; but no further. In 

 Plagiaulux there are as many as four premolars ; while in Thyla- 

 coleo the enormous development of the solitary premolar or carnassial 

 is effected at the expense of the rest of the premolars, which are 

 suppressed, and of the tubercular teeth, which are dwarfed. In the 

 former, as pointed out in my earlier description, " the premolars are 

 inordinately developed, while the true molars are dwarfed and rudi- 

 mentary in proportion." The operation of the well-known law of 

 Anamorphosis or Balancement is visible in both. But examples of 

 it are everywhere seen throughout animated nature, in the same 



* Odontography, vol. i. p. 389. 



t Phil. Trans. 1767, vol. Iviii. p. 38. 



2b 2 



