PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
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are those correspondences in the upper carnassial, and are unmistakable. A broader 
well-defined prominence on the fore part of the inner surface of the crown of the lower 
sectorial (Plate XII. fig. 11, r) leaves a part anterior to it (ib. a) representing the anterior 
basal talon, chiefly marked or extended upon the inner surface of the fore part of the 
crown in the lower carnassial of Felis and Hyaena. The indications of vertical elevations 
of enamel are more feeble in the lower than in the upper sectorial, and are chiefly seen 
at the basal part of the inner surface. The notch at the middle of the trenchant border 
in the less worn lower carnassial (Plate XII. fig. 11) clearly indicates divisions resembling, 
though more feebly marked, the anterior and posterior lobes of the homologous tooth in 
the placental Carnivora (ib. fig. 12). 
The absence of the anterior transverse expansion, and the straight line described by 
the trenchant border of the lower sectorial of the Potoroos, is, at least, as strongly marked 
in the lower jaw (ib. figs. 8, 10, 13) as in the upper one (Plate XI. figs. 17, 18). In 
juxtaposing the specimens of the homologous teeth in Thylacoleo and any Potoroo for a 
true deduction of comparative similarity and difference, “ one sees at once that the great 
cutting premolar of the Hypsiprymni or Rat-Kangaroos is” not “a miniature of that of 
Thylacoleo ” *. And, if it were, the function of such sectorial could not be deduced from 
mere shape, but from the nature of the other teeth wherewith it is associated, and the 
modifications of the jaws by which such dentition was worked. 
The student in reading of the “ great cutting premolar of the Rat-Kangaroos” must 
bear in mind that the epithet is relative. Where such tooth is greatest in those vegeta- 
rians it is small in comparison with its homologue in Thylacoleo. The difference of 
shape, direction, term of growth, and of every character meaning function is still greater 
and more obvious in the incisors of the Diprotodonts compared than in the sectorials ; 
and the degree and kind of difference shown by Thylacoleo testifies to the carnassiality 
of the main representative tooth of the molary series. 
Against the association of that great carnivore with the Poephaga “(= Macropoda, 
V. d. H.),” there are opposed not only the differences above demonstrated in the homo- 
logous sectorial teeth, but the absence of the third pair of upper incisors and the pre- 
sence of premolars in advance of the sectorial one in both jaws of Thylacoleo. It will 
be admitted by candid readers of both my Papers on that genus that I have been reti- 
cent of conjecture or assumption ; but I venture to say that when the limbs of Thyla- 
coleo are restored they will not be “ macropodal,” not minimized at the fore part and 
maximized at the hind part of the body, for bipedal saltatory actions to bear it swiftly 
away from carnivorous pursuers, or to carry it far abroad from pasture to pasture and 
from scrub to scrub in quest of vegetable food, but that they will agree in the main with 
the limbs of Leo , Thylacinus , and Sarcophilus. 
Pursuing the comparison of Thylacoleo with other Diprotodonts , we may at once dismiss 
the arboreal Phascolarctidce , with a trenchant premolar (at least in the young Koalas), 
on the same grounds as those on which the Poephaga are rejected from the association. 
* XII. P . 310. 
2 m 
MDCCCLXXI. 
