TOOTH-GENESIS IN THE CAVIIDA. DATS 
gum, somewhat to its lingual side. The anterior cheek-tooth of 
the adult consists of two plates, an external and an internal, 
separated one from the other by a deep oblique cleft, so deep 
that the plates are but slightly connected by their bases and 
are easily separable. The position of the tooth is partially rotated 
through an angle of about 45°, so that the external and more 
prominent cone lies antero-externally, the internal being postero- 
internal. When examined from the internal surface, the apex of 
the outer cone appears to be folded inwards so as to reach the 
apex of the internal cone, but without being fused with it. The 
folding gives rise to a transverse groove crossing the apex of 
the external cone. 
Fig. 5. 
A. View of teeth in Left Upper Jaw (Stage 4), seen from the inner side. 
B. Crown surface of Deciduous Tooth. 
C. ss = Successional Tooth. 
10), ss 5 Fourth Cheek-tooth. 
The inwardly-folded apex is supported by a vertical ridge upon 
the inner face of the external cone, so that this cone would on 
horizontal section have a triangular shape, the curved base 
being external, the apex internal with a slightly backward 
inclination, which is applied to, but not fused with, the outer 
face of the internal cone towards its posterior margin, as seen 
in fig. 5 C. It lies in a separate capsule of its own, quite 
distinct from that of the deciduous tooth, which is nearer the 
margin of the gum. The latter has not undergone any rotation, 
is very minute and its cusps complete, the enamel not having 
disappeared from their apices. 
The third and fourth cheek-teeth had already assumed the 
characters of adult teeth, the former being the larger. 
With regard to these teeth, I would note the absence of 
tubercles from the crown-surface, the enamel having partially 
