DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 521 
has an irregular appearance in many sections, owing to the 
presence of irregular appendages derived from the “ neck” 
portion of the dental lamina. 
Stage XIII—P. nasuta: pouch specimen. 
Length from tip of snout to root of tail ‘ - 180 mm. 
Length of skull . A ; : Gnas 
It will be seen from fig. 75, representing the upper jaw of 
this stage, that all the antemolar teeth (except p®) have cut 
the gum, and most of the general characters of the adult den- 
tition are recognisable. Of the molars two in the upper jaw 
and three in the lower have broken through. The very small 
dp is seen occupying the slight interval between p2 and m1. 
The Anlage of pz in the lower jaw is shown in section in 
fig. 74. It is now a well-developed cupped enamel-organ, 
and, in one of the two series cut, the dermal papilla is much 
larger than in the section figured, filling up the whole of the 
somewhat deeper cup of the enamel-germ. 
In the latter the stellate tissue of the middle layer is now 
well developed. In fig. 74 it will be observed that the enamel- 
organ is now in process of constriction off from the lamina, 
whose free end is already beginning to project as a new resi- 
dual lamina (rdl.). That this interpretation is the correct one 
is proved by reference to Leche’s figs. 140 and 142 (here- 
with reproduced for comparison as figs. 76 and 77), showing 
the corresponding enamel-organs of p? in Phascolarctus. 
In connection with the latter a very evident and swollen 
residual dental lamina has anew developed itself by the side 
of p3. This, according to Leche, provides for the possibility 
of the production of a tooth of the third (his “ fourth ”’) denti- 
tion. We believe that this possibility must not be lost sight 
of, but in the meantime we prefer to point out that the regular 
development of such an Anlage as has been discovered and 
figured, both by Leche and by ourselves, by the lingual side 
of p&, serves in the most striking way to confirm our view of 
the homology of p? to the other adult antemolar teeth, whose 
residual dental lamine (‘‘Hrsatzleisten ”’—auct.) are there- 
