506 J. T. WILSON AND J. P. HILL. 
The canine is not so far advanced as the incisors. It is 
smaller, and its dentinal covering much thinner. 
Beside p; a trace of the free residual portion of the dental 
laminais still to be seen. This tooth is further advanced than 
the canine, for both its dentinal and enamel layers are thicker. 
Beside pz there is a small but distinct residual lamina pro- 
jecting beyond the point of attachment of the connecting 
bridge. The tooth is somewhat less advanced than pz. 
The third premolar region is similar to that in the upper 
jaw. In one place there is a very distinct indentation of 
the thickened lamina on the lingual side of dpz. This 
indentation persists through a considerable number of sections, 
and is filled by loose connective-tissue cells, the whole being 
surrounded by a condensed connective-tissue capsule (fig. 64). 
This represents the earliest trace of the definitive papilla of pz. 
In the posterior molar region the anterior cusp of mz is 
now calcified. The tooth is still attached to the persistent 
lamina, which is prolonged beyond the point of attachment as 
a residual lamina. 
Stage VII.—P. nasuta: mammary feetus. 
Length from vertex to root of tail . ‘ . 56 mm. 
Head length . : : ; . 25 
The incisor region of this stage derives some special interest 
from comparison with the previous stage. On the whole the 
teeth are somewhat larger, indicating greater maturity. But 
75 forms an interesting exception. Here it is not yet calcified, 
although it was quite strongly calcified in Stage vi. It is, in 
fact, only slightly ahead of the condition in Stage v. Further- 
more its topographical relations differ from those seen, not 
only in Stage v1, but also in Stages v and viii, all of which 
agree with each other. 
Prior to our Stage v there is no overlapping of the posterior 
incisors, which are small; and 24 is simply placed in front of 
i5, But in later stages the enlargement of the upper 
incisor teeth relative to the size of the jaw causes very 
considerable overlapping, and in Stages v, vi, and vir the 
