DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 515 
anterior sections of dp*, which cut the apical part of the 
tooth somewhat obliquely, show that it has already cut the 
gum. As it is traced backwards the crown recedes from the 
surface, and its crown assumes the appearance shown in the 
figure (fig. 67). 
More posteriorly it is narrower than in the drawing, but is 
still much elongated. In this stage dp® is seen to be a very 
much smaller tooth than the anterior premolars. It does not 
appear in the sections until behind the plane of the maximum 
development of p2, but nevertheless the posterior part of p2 
extends backwards slightly behind it, being still visible when 
dp> has totally disappeared. 
The character of m2 is shown in fig. 70. It exhibits only a 
very slight advance on the preceding stages of the same tooth. 
Lower Jaw.—In sections passing through the anterior 
tip of 7; the same rudimentary enamel-organ is encountered 
as was noted in Stages 1v—vit. It is, however, more irre- 
gular than in Stage vir, and is evidently undergoing resorp- 
tion, without having shown the least trace of calcification. 
The tip of 7; has now grown far forward by the labial side 
of z;, and has insinuated itself between the latter tooth and 
its vestigial milk predecessor diz. This is a clear case of 
relative displacement of ¢; similar to that which we have 
shown to occur in the case of 2; with reference to the rudi- 
mentary enamel-organ morphologically in front of it. 7, at 
this stage shows the now calcified posterior secondary cusp 
very distinctly. di; is in statu quo as regards its struc- 
tural characters, only its relative topographical position is 
slightly altered by forward growth of iz. 7; appears further 
back by the labial side of 7,. It bears the same topographical 
relation to 7; as the latter does further forward to 7;, so that 
all trace of the early peculiarities in the relative situation of 
these teeth is now lost. 
The basal part of 7; may be traced far back, lingually to, 
and in a deeper plane than, 7; and iz, all three appearing to- 
gether in the sections throughout a considerable extent of the 
anterior part of the jaw. 
VOL. 89, PART 4,—NEW SER. NN 
