167 



form tooth not preceded by incisors can be carnivorous. All phytophagous Marsupial 

 genera have a pair of developed incisors, approximated and placed collaterally in the 

 lower jaw as in placental Rodents; ergo, a Marsupial fossil mandible with such incisors 

 must be of an herbivore." But it is affirmed : — " the incisors of Plagiaulax are framed, 

 in regard to number, order of suppression, collateral position, and relation to the premo- 

 lars, in exact correspondence with the type of the Marsupial herbivores, such as Halma- 

 turus, Hypsiprymnus, and Phascolarctos, and wholly at variance with the Carnivorous 

 type "*. And if considerations of the shape of the incisor, modification of its working end, 

 angle of its projection, degree of curvature of the tooth, evidence of its temporary growth 

 or otherwise be set aside, the same may be affirmed of the lower incisors of Thylacoleo. 



Any one enjoying a sense of confidence in the impossibility of a modification of the 

 diprotodont type of Marsupial dentition for carnivorous habits may well dispense not 

 only with a consideration of all those characters of the teeth in question which truly 

 point to their function, but also of the modifications of size, shape, and number of the 

 molar teeth associated with such pair of lower laniariform incisors. 



I am not cognizant of any facts subversive of the Cuvierian principle as to the teeth 

 which should first be observed in an unknown fossil by the palaeontologist in quest of 

 the nature of its food, and I cleave to the belief of their primary importance as throwing 

 light on the problem to be solved. 



I have qualified Dr. Falconer's generalizations even when restricted to existing Mar- 

 supials, as " alleged." Let me recall to the recollection of his followers some of the 

 instances which invalidate the general averments adduced to show that Thylacoleo and 

 Plagiaulax must be herbivorous because diprotodont. 



The small insectivorous Marsupial Tarsipes combines with its two " well-developed, 

 long, slender, and pointed lower incisors "f, minute molars unfitted, as in Plagiaulax and 

 Thylacoleo, for mastication of vegetable food. Its simple alimentary canal, only exceed- 

 ing the entire length of the animal by about one-half, is " destitute of C8ecum"j, as in 

 the small Polyprotodont Phascogale^. "When intent upon catching flies it would sit 

 quietly in one corner of the cage, eagerly watching their movements" ||. 



According to the "fundamental principles which comparative anatomy supplied" to 

 Dr. Falconer " for his guidance " (but which principles he nowhere defines), Tarsipes, 

 like Thylacoleo and Plagiaulax, having " a pair of developed incisors approximated and 

 placed in the lower jaw collaterally," should have been " phytophagous." 



Let us test the contrasted conditions of the generalization as to incisors by another 

 appeal to living Nature. " The Root-feeding Dalgyte"% or Australian " Native Rabbit 11 

 (Peragalea lagotis), is a miscellaneous eater. The specimen in the Zoological Gardens 



* X. p. 352 ; XL p. 435. t Waterhouse, ' Natural History of Mammalia ' (Marswpialia), p. 342. 



% Op. at. p. 343. 



§ Owen, Art. " Mmrswpialia" Cyclopaedia of Anatomy, vol. iii. p. 300, fig. 122 (Phascogale flavipes). 

 \\ Gould, ' Mammals of Australia,' vol. i. (Tar&pes rostratus). 

 *fi Gould, ' Mammals of Australia,' vol. i. Introduction, p. xvii. 



8* 



