TRANSACTIONS OF THE ROYAL MICRO- 
SCOPICAL SOCIETY. 
DESCRIPTION OF PLATES V & VI, 
Illustrating E. Ray Lankester’s paper on tlie Structure of 
the Tooth in Ziphius Sowerbiensis ( Micropteron Sower - 
biensis, Eschricht), and on some Fossil Cetacean Teeth. 
PLATE VJ 
Fig. 
1. — Part of a transverse section of the upper part of the tooth of Microp- 
teron Sowerbiensis , in the University Museum, Oxford, c, Cement ; 
g, globular matter, with interglobular spaces ; d , dentine ; o-d , osteo- 
dentine. 
2. — Portion of another section, a little nearer the base ; letters as before. 
3. — Cement of the same tooth ; natural size of lacunae, 3 £gth — T 3 M th of 
an inch, a, Small longitudinal lacunae. 
4. - — "Dentinal tubules emerging from the opaque globular mass, with its 
interglobular spaces or dentinal cells. 
PLATE VI. 
1. — Tooth of Micropteron Sowerbiensis , natural size, a b, Line of the 
alveolus. 
2. — Longitudinal section of the same, a, Line of microscopic sections ; 
d , dentine; o-d, osteo-dentiue ; g, globular matter; c, cement, 
3. — Half of a transverse section ; letters as before. 
4. — Osteo-dentine of a fossil tooth. 
5. 6. — Osteo-dentinal cavities of fig. 4 in section ; natural size, Ath— ^ 5 th 
inch. 
