232 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
Fig. 5. 
Front Hew of mandible and teeth 
{Phascolarctos), three-fourths nat. size 
(after Professor Flowek, XII. p. 313, 
fig. 4). 
by Professor Flower for comparison (in XII. p. 313, fig. 4), copied in Cut, fig. 5, appears 
to 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 
the front view of the mandible (Plate XIII. fig. 3). They 
may be blunted by use, or the point may be broken off, 
as in figures 1, 4, Plate XIII., 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 6, i, where the working surface of the lower 
incisor of the phytophagous diprotodont Marsupial may be compared with that of the 
zoophagous one (Plate XIII. 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 XI. fig. 3, m i). 
Then, as regards the lower jaw (Plate XIII. fig. 1), the molar (m i) following the carnas- 
sial (p 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 \ 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 XI. 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 
