PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
249 
their dentition and shape of mandible than they do any other family of diprotodont 
Marsupials* * * § . From the characteristic reduction in size and number of the molar teeth 
I have associated them as members of a “ paucidentate ” family or section. 
To which of the existing families of Diprotodonts is the paucidentate one most 
nearly allied 1 Thylacoleo best lends itself to the solution of this question, its maxillary 
as well as mandibular dentition being now, I may affirm, accurately determined. It 
is highly probable, from the close conformity of Plagiaulax to Thylacoleo in the pecu- 
liarly and extremely modified dentition of the lower jaw, that the maxillary teeth also 
resembled those of the larger diprotodont carnivore. Of this the dental formula is : — 
i. 
2—2 
1 — 1 ’ 
c. 
1—1 
0 — o’ 
p. 
4—4 
4— 4 5 
m. 
1— i . 
2 — 2 * 
= 30. 
No existing Diprotodont offers a like formula. That of the Poepliaga\ departs further 
than in most other diprotodont families, because there is no tooth interposed between 
the incisor and sectorial in the lower jaw, and in most Kangaroos not more than two 
are developed between the front incisor and sectorial in the upper jaw on each side, the 
two intervening teeth being both incisors — both anterior to the maxillo-premaxillary 
suture. Hypsiprymnus and Pettongia have a small canine in that suture, and two incisors 
between the larger front incisor and the sectorial in the upper jaw, but no teeth in that 
interspace in the lower jaw (figs. 17, 18). Of the more important true molar teeth 
(id. ib. to 1 - 4 ), the first three have “ a quadrate form, presenting four equidistant blunt 
tubercles which are joined in pairs by transverse ridges, but with these ridges less ele- 
vated than the points of the tubercles ; there is a slight trace of the band of the tooth ” 
(‘cingulum’ of my ‘Odontography’) “on the front and back part of each molar as in 
Macropus. The hindermost” (fourth) “molar is generally small, almost round. Cases 
occur in which the last molar tooth is absent ; and, what is more extraordinary, I have 
observed an extra tooth on each side of the upper jaw in a species of Piypsiprymnus"%. 
Thus in these mixed feeders, but with the vegetable diet predominating, the molar 
teeth adapted to such diet are never fewer and commonly more in number than in the 
most typical placental Herhivora. In relation, apparently, with the drier and tougher 
vegetable fibres of Australia, the premolar is trenchant and strengthened by vertical 
grooves and ridges. In one of the New Guinea Tree-Kangaroos ( Pendrolagus dorco- 
cephalus ) this trenchant tooth (p, fig. 16) is proportionally larger than in the Australian 
Potoroos and Bettongs, but the light-giving teeth (the true molars) “are conformable 
with the Macropus type”§. 
* Dr. Falconer asserts, “ Thylacoleo and Plagiaulax may be regarded as being as wide apart among the Mar- 
supials as the two former ( Machairodus and Moschus) are among placental Mammals.” — X. p. 358 ; XI. p. 442. 
t I hold by this term, preferring it to the subsequently propounded one, Macropocla, of Van der Ho even, 
because the latter is equally applicable in its descriptive sense to the long-legged, saltatory Polyprotodonts. 
+ Waterhouse, ‘A Natural History of the Mammalia’ ( Marsupialia ), 8vo, 1845, p. 194. 
§ Ibid. p. 182, pi. 10. fig. 3. In my ‘ Odontography’ I showed that the “ maximum of development of the 
trenchant premolar was attained in the arboreal Potoroos of New Guinea ( Ily psip rymnus ursinus and Hyps, 
dorcocephalus), in the latter of which its antero-posterior extent nearly equals that of the three succeeding molar 
