too broad and pronounced to be misunderstood. The herbivorous Marsupial selected 

 by Professoi Flower for comparison (in XII. p. 313, fig. 4), copied in Cut, fig. 5, appears 

 in have a similar carnassial (p); but this appearance is 

 due to the foreshortening of the series of the grinding- 

 teeth of* the Koala. 



My business here is simply to set forth the facts which 

 guide to a right conclusion, and to put them as correctly 

 as I am able. The incisors of Thylacoleo are neither 

 truncate nor flattened by attrition at their ends; their 

 character, from nature, is given, of the natural size, in Front view of mandible and teeth 



. „ . P ... , /T ,, . TX7 - ox (Phascolarctos), three-fourths nat. size 



the front view of the mandible (Plate IX. fig. 3). Ihey (aftcr Pro fe 8SO r Flowbe, XII. p. 313, 

 may be blunted by use, or the point may be broken off, 4 )- 



as in figures 1, 4, Plate IX., from the photograph No. 10. The laniaries of an old 

 Lion usually show the same effects of usage. Professor Flower gives a front view of 

 the incisors of Phascolarctos, and a side view of the incisors of Hypsiprymnus ; but a 

 view of the working surface, from which the best idea can be formed of the use to which 

 such incisors, in the two Marsupial herbivores, are put, is not given. I have supplied 

 this omission in the upper figure of Cut 0, i, where the working surface of the lower 

 incisor of the phytophagous diprotodont Marsupial may be compared with that of the 

 zoophagous one (Plate IX. fig. 7). 



Returning to Cuvier's test of the diet of an extinct animal, which test gives the use of 

 the long anterior teeth, whether canines or incisors, of such animal, I may recall atten- 

 tion to the single, small, — one may truly say, viewing the enormous carnassial against 

 which it abuts — minute tubercular in the upper jaw of Thylacoleo (Plate VII. fig. 3, m i). 

 Then, as regards the lower jaw (Plate IX. fig. 1), the molar (m i) following the carnas- 

 sial (j> i) has the anterior half of the crown compressed transversely, the sides converging 

 to a trenchant margin: this approximation to the form of its homologue in Felines, 

 from the close and extensive abutment of the tooth against the upper carnassial, forms 

 a continuation of the shear-blade structure, and gives the lower blade an extent equal 

 to that of the larger carnassial above. The tubercular part of m i below forms a mere 

 basal talon to the carnassial part of that tooth, whilst m 2 is a truly minute tubercular, 

 and, seemingly, soon lost. 



The demonstrated structure of the laniaries of Thylacoleo is in harmony with the 

 zoophagous work which the molar teeth are plainly designed to transact. 



Now. being solely desirous to test Cuvier's principle in reference to the approximate 

 pair of long incisors of Phascolarctos, I subjoin what is essential to such test, and what 

 Professor Flower omits, viz. a side view of the dentition of the Koala, reduced one-half, 

 together with a view of the grinding-surface of the molar teeth, natural size (Cut, fig. 6), 

 corresponding with those of the Thylacoleo shown in Plate XL fig. 3, Plate XII. fig. 3. 



The tooth (p 4), probably homologous with the carnassial of Thylacoleo, and that 

 which most resembles, or rather least differs from, it in the shape of the crown, occupies 

 less than one-eighth of the dental series in Phascolarctos, in Thylacoleo it occupies nearly 



