SUCCESSION OF THE TEETH IN THE DASYURIDAE. 
461 
3. Fossil Eutherian Mammals, showing an intermediate degree of tooth-change 
between the modern Eutheria and Metatheria, would obviously be highly favourable to 
the views now put forward as furnishing some of the intermediate stages corresponding 
to those above called Stages VI. and VII. 
4. The discovery of a rudimentary successor to any of the premolars or other teeth 
now unchanging in the Marsupials. This also would be fatal, as it would show that 
it is, after all, the permanent and not the milk set of teeth which is superadded. 
It is, however, possible that at the first commencement of the assumption of a fuller 
change by the Marsupial ancestors of the Placental Mammals the Marsupial characters 
of inflected jaw, imperfect palate, &c., were retained for some time after the 
rudimentary tooth-change had been improved upon. In some Mesozoic fossils, 
therefore, the Metatherian osteological and Eutherian dental characters may be found 
to have co-existed for a certain time without invalidating the views above expressed. 
5. Fossil Edentates with more premaxillary teeth than one, or, in other groups than 
true Dasypus, with any at all, would be confirmatory of the suggestion that the 
Edentates descended from the same Stage I. as other Mammals, and had lost four, or 
all, of their original number of five premaxillary teeth. 
6. Further instances of the atavistic recurrence of usually absent teeth in all groups 
of Mammals are much needed for the working out of the tooth-homologies in the 
different groups. 
On any of these points it will be most important to have information, and I hope 
that such, whether favourable or adverse to my views, will, if correct and properly 
authenticated, be soon forthcoming. 
Explanation op the Plates. 
PLATE 27. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
Fig. 
1 . 
2 . 
3. 
4. 
5. 
6 . 
7. 
Anterior cheek-teeth of Phascologale virginice. 
,, ,, ,, penicillata. 
,, ,, ,, thorbeckiana. 
,, ,, ,, apicalis. 
,, ,, Dasyurus viverrinus. 
This series shows the gradual decrease in size, and ultimate loss, of the 
last premolar (pm 4 ). 
Anterior cheek-teeth of Phascologale penicillata, showing the milk pm 4 in 
position, and its successor above it still buried in the bone. 
Anterior cheek-teeth, left side, of abnormal specimen of Phascologale dorsalis, 
showing atavistic second premolar (pm 2 ) in position. 
