DEVELOPMENT AND SUCCESSION OF TEETH IN PERAMELES. 499 
appearance of this tooth (except that it as yet shows no calci- 
fication) and its relations to the liberated lamina are exactly 
as described and figured in the upper jaw, no further par- 
ticulars need be given. 
Behind the third premolar region the lamina (still con- 
tinuous throughout with the oral epithelium) undergoes 
further deepening and becomes continuous with the large 
enamel-organ of the first molar, which is larger and more 
complicated than the corresponding upper tooth. Here the 
dental lamina is for some distance separated off from the oral 
epithelium. A residual dental lamina is well developed, as in 
the upper jaw, and its freely projecting margin is moderately 
swollen. Towards the posterior end of m; the dental lamina, 
now unconnected with the tooth, is also for the most part 
separated off from the oral epithelium, and is continued into 
the region of the second molar. Here again it shows a labial 
connecting strand (“ Verbindungsbriicke”) joining it to 
the enamel-organ of mz; whilst its free marginal portion 
forms a large residual dental lamina, just as in the upper jaw. 
Towards the hinder end of mz the dental lamina again becomes 
connected with the oral epithelium, exhibiting near its point 
of connection a somewhat elongated labial laminar outgrowth. 
Further back the lamina entirely loses its connection with the 
oral epithelium, becoming more deeply placed among the con- 
nective tissue of the jaw. Its distal portion is converted into 
the papillated enamel-organ of mz, whose posterior end forms 
the present termination of the lamina. The liberation of a 
residual dental lamina by the side of mz has already been par- 
tially effected. 
Stage V.—P. nasuta: mammary foetus. 
Length from vertex to root of tail . é . 37mm. 
Head length ‘ : : ass 
Coronal and horizontal series examined. 
This stage represents only a slight advance on the preced- 
ing. 
Upper Jaw.—All three first incisors are now well developed, 
voL. 389, PARY 4.—NEW SER. MM 
