492 J. T. WILSON AND J. P. HILL. 
be borne in mind. The plane of the section lies too high to 
intersect the main mass of p2, which is relatively low and 
transversely elongated. Still the obliquely cut anterior por- 
tion of the segment of the lamina figured really corresponds 
to the tapering posterior end of p2, which is higher (deeper) 
than the rest of the Anlage. In like manner the narrowing of 
the dental lamina, seen in the figure as occurring towards dp, 
is to be explained not as an actual diminution of the sectional 
area of the lamina, but only of its width at this horizontal 
level. And if sections through exactly the same region but 
in a higher horizontal plane be examined, it will be found 
that, when the fundus of the free dental lamina close beside 
dp® is cut through, its sectional outline is quite comparable to 
that seen further forwards. There is, in short, just such a 
gradual heightening of the lamina, when it is traced backwards 
into the dp= region, as there is in front of the premolar region 
when the lamina is traced forwards from p+ towards the 
canine. 
It has already been shown that a residual dental] lamina is 
liberated by the side of dp? at a very early period, and that 
this soon becomes thickened at its margin and “ bud-like” on 
cross-section. It is from this liberated lamina that p? takes 
its origin in Perameles. 
Even in Petrogale, upon which Woodward chiefly founds 
his case, we cannot allow that the conclusion that p> (his p+) 
is morphologically in front of dp> (his dp*) is at all so in- 
evitable as he regards it. The proofs drawn from the mere 
appearance of the dental lamina in transverse sections are, in 
our opinion, of very little value. A quite similar development 
of the deeper part of the dental lamina, and an identical 
development of loose and stellate-like epithelial tissue in its 
interior, may frequently be met with where there is no 
question of the presence of a tooth at all. 
It is only the definite localised elevation, sharply limited 
fore and aft, figured in the drawing of a wax model of this 
region of the lamina in Petrogale which seems to us atall a 
formidable evidence of the view put forward. And even this 
