1G2 



that the tooth is essentially alike in Plagiuulax" (as Professor Flower contends that 

 it likewise is in Thi/lacolco*). " If, therefore," proceeds Dr. Falconer, " the function 

 is to be deduced with such facile certainty from the mere form, the premolar of 

 Hypsipryrmu8 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 Mataupialia the Ruminants of the placental Mammals. With this fact before us, 

 is it likely that the premolars of Flag i aid ax and Thylacoleo 'were applied to cut and 

 divide flesh' ?"f 



To this I reply; consider the difference of the molar teeth following the trenchant 

 one in Plctgiaulax and Ilyjisiprymuus respectively, and the true solution will be given %. 



Interrupted and continuous applications of Teeth. — The deduction of the carnivorous 

 nature of the extinct Marsupials in question was drawn not from shape merely, but 

 from correlation of teeth. The " arbitrariness," if such quality be predicable of the 

 conclusion, is applicable to the guiding principle, not to the palaeontologist confiding 

 therein. If reference to confirmatory and collateral facts was omitted in the Papers of 

 1859 and 1869, it was under the belief of their being the common property of the 

 interpreters of fossil remains. 



In the adoptively modified dentition of the class Mammalia the differently shaped 

 teeth are put, some to occasional and interrupted, others to continuous use. The 

 incisors of the child biting a piece of bread and butter exemplify the first functional 

 character ; the molars which pound the piece bitten off, the second. These incisors are 

 trenchant or sharp-edged like the premolar of a Bettong or the carnassial of a Cat ; 

 their action in the human subject leaves a clean semicircular border of the bitten slice. 

 The teeth, of whatever kind, incisors, premolars, or molars, which have the continuous 

 work show its effects by an abraded surface. Those which have the occasional and in- 

 terrupted work show little or no indication of such. The laniaries of Camicora, when 

 they have pierced and lacerated the prey, have done their work ; the gnawing off of the 

 pieces of flesh adapted for the imperfect tubercular mastication and for deglutition is 

 effected by continuous action of the sectorial blades, the mouth being turned sideways 

 to the food, as may be seen in the Felines and other CarMvora which have the largest 

 and best-shaped carnassial teeth. Such action and application of these teeth are exem- 

 plified by the clean-worn, smooth, oblique surface sloping in the opposed blades down 

 their opposite and opposed sides. 



The same functional character, relating, that is to say, to " time" or " prolongation of 

 use," is indicated by the incisors. Those in Thylacoleo and Plagiaulax show no evidence 



* XII. p. 310. "The great cutting premolar of Thylacoleo bears no real comparison with the carnassial 

 tooth of the Carnivora, but with the compressed premolar of the Hypsiprymni. n — lb. p. 316. 

 f X. p. 356 ; XI. p. 440. 



X Dr. Faixoxer, indeed, does strengthen his attack by calling in the argument from correlation ; but he selects 

 a different tooth from that of the Cuvierian principle : — " When this conclusion as to the herbivority of Plarji- 

 oulax" and ThylaedUo " from similar trenchant characters of premolars with those of ffypsiprymnut is coupled 

 with the obviously phytophagous type of the incisors, the conviction will be confirmed." — X. p. 357 ; XJ p 440. 



