DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 503 
a considerable number of sections, and evidently answers to 
the labial outgrowth figured in connection with Stage iv 
(fig. 57) as a vestigial diz. It is now in process of absorption, 
and apparently has never shown any sign of calcification. 
From its first appearance in Stage 11 it has never attained 
the dignity of tooth-like differentiation of structure. 
Behind the third incisor region the dental lamina again 
deepens, though its connection with the oral epithelium is 
interrupted for a time. Its free margin thickens, and is con- 
tinued directly into the canine Anlage, but very soon is 
partially freed from it, being prolonged as a residual dental 
lamina. The canine enamel-organ is now bell-shaped, and as 
yet is uncalcified. 
In the anterior premolar region the oral connection of the 
dental lamina is frequently interrupted ; p; is slightly calcified, 
while pz has as yet developed no dentine. 
The deciduous premolar and its relations to the Anlage of 
pz resemble those in the upper jaw, except that the pz thick- 
ening does not exhibit the peculiar indentations present in the 
upper jaw, and that dp is distinctly less advanced and is still 
uncalcified ; in fact, it appears slightly less mature than in the 
preceding stage. 
The molar region shows an advance upon the condition in 
the lower jaw of Stage rv, in that mz is now a fairly large 
and deeply papillated tooth showing traces of differentiation 
of cusps. A well-developed residual dental lamina is present 
on the lingual side of each molar, and extends far beyond the 
epithelial connection with the enamel-organ. 
Stage VI.—P. nasuta: mammary foetus. 
Length from vertex to root of tail . : . 44mm. 
Head length : ‘ ; . 24 
= ” 
Lips now separated to form the ‘‘definitive Mundspalte.” 
This stage exhibits a marked advance upon the last in 
regard to tooth development. In it we may be said to en- 
counter for the first time throughout the adult form of the 
various teeth, except in the most posterior molar region all 
