538 BALANODON. 
dulated, divide and subdivide dichotomously in their 
course to the periphery of the axis, where they terminate 
in very fine irregularly bent ramuli; some forming loops, 
others dilating into minute calcigerous cells. The den- 
Fig, 228. 
‘ | 
== = == = LA 
sty 
Microscopie structure of dentine ; magnified 500 diameters. Balenodon. 
tinal cells were very conspicuous in many parts of the 
section, of a sub-circular form, and about 3524>th of an 
inch in diameter. 
The clear basis of the cement is almost colourless where 
it fills the outer indentations of the dentine, and the ra- 
diated cells are fewer here: in the rest of the entire 
thickness of the cement they (fig. 229, ¢ c) are very abun- 
dant, and arranged at intervals of about thrice their own 
diameter, which diameter is about ;>4<th of an inch. 
The cetaceous character of the cement is manifested by 
the numerous and sub-parallel cemental tubes, (fig. 229, ¢,) 
which run from the outer part of the cement towards the 
dentine, near which they terminate by fine ramifications, 
communicating with the radiating tubular prolongations 
of the cells. The thick cement is also traversed by vas- 
