566 MR. M. F- WOODWARD ON [May 5, 
probably would not cut the gum, although at times it may do so 
(Thomas, 23). 
There is a complete replacement of the lower incisors, but the 
successors develop at very different times, pi.1 and pi.3 maturing 
long before pi.z. Consequently in my foetus no sign of the future 
pi.2 was visible, although the enamel-organs of pi.1 and pi. 3 were 
Just recognizable. Asa matter of fact pi.2 is, I believe, the last 
permanent ante-molar tooth to cut the gum, appearing soon after 
the eruption of ppm.3- 
The Canines. 
The milk-canines possess single roots, and are but slightly 
larger than the incisors (fig. 13); whereas the permanent canines 
are very large teeth, with pointed crowns, and each provided with 
two fangs. 
The Premolars. 
Pin. 1 
Pm. 1 
case these teeth would appear to belong to the milk-dentition, for 
there is present on the lingual sides of their enamel-organs well- 
marked continuations of the dental lamina, precisely similar in 
their relationship to that seen by the side of de., which gives rise 
to the enamel-organ of pe., only the inner ends of the former are 
perhaps a trifle less swollen. It is just possible that these 
structures may give rise to the enamel-organs of successors at a 
late period, tor the first premolar of the adult skull appears to be 
a slightly stonter tooth than that of the young animal. 
The lingually situated dental lamina in both the upper and 
lower jaws gets smaller and more irregular behind pm. 1, but soon 
becomes definitely swollen, and forms the commencement of an 
enamel-organ (figs. 11 & 12, ppm.2); this, from its position and 
backward condition, is evidently that of a successional tooth, viz., 
ppm. 2. This identification is rendered more certain by finding on 
the labial side of this structure a small calcified tooth (dpm. 2), 
devoid of enamel, but possessing a much reduced enamel-organ |. 
In the case of the upper tooth this reduced enamel-organ is 
attached to the gum close to, but independent of, the swollen, 
lingually-situated dental lamina above reterred to(ppm.2). In the 
lower jaw, however, the enamel-organ of the vestigial tooth 
(fig. 12, dpm. 2) is apparently attached to the corresponding lingual 
swelling of the dental lamina, thus exhibiting the normal relation- 
ships of a milk and a replacing tooth. 
The deciduous 2nd premolar is then reduced and early lost, 
while its successor is somewhat precociously developed (cf. fig. 11, 
are said to be present in one dentition only. If this be the 
1 In a preliminary note, read before the British Association, 1895 (2'7), 
I stated that there were traces of five premolars in Gymnura: this is not the 
case ; the error arose through a misinterpretation of a curious development of 
the pulp of this tooth, dpm. 2 (see Pl, XXIV. fig. 11, p), which was mis- 
taken for a successor. 
