72 
ROOM XL 
NaTo Hist.. 
ticliopora) are allied to these by some characters, but 
their cells are simpler and placed in three series on each 
side of the coral, those of the two lateral series being 
much smaller than the central one. 
The cells in the rest of these corals are furnished 
with regular and distinct rays, like those of the first 
group. In a few of these, as the White Coral ( Ocu - 
lina) t the mass is subcylindrical and arborescent, and in 
others, as the Star-stones ( Astrced)> its form is globular 
or expanded. 
In some of the Star-stones the axes of the cells are 
solid and produced (Astrcza pleiades ), so as to resemble 
in that respect the fossil Sarcinulae and Stylinse, peculiar 
for the centre of their stars being produced. The 
Explanariae ( Explanaria ) only differ from the star- 
stones by the mass being more expanded and foliaceous* 
or by the under surface being free and destitute of stars. 
The Sarcinulae and Lithodendrons are very like the 
star-stones, but the cells are cylindrical and prominent, 
and instead of being arranged side by side in one mass, 
they are, in these genera, united together by cross bands 
of calcareous matter, between which there is often placed 
a cellular structure, and in their young state the cells are 
prominent, and spring from a flat calcareous expansion. 
Some fossil genera have much the appearance of the 
Star-stones. Their cells are aggregated, side by side,, 
forming a rounded mass, but they are quite separate 
from each other; these masses increase in size by new 
cells springing from the centre or margin of the older 
cells, as in the Acervulariae and Strombodes. It may 
be remarked, that in the thin extremities of the Arbo¬ 
rescent Corals, the cells often appear proliferous from 
the side of each other. 
The Cases 9 to 12 contain the Polypiaria. 
The Polypes of this class differ from the Sea-Ane¬ 
mones by the mouth being provided with only a single 
series of long tentacula, by the body being more slender, 
and by the cells which they form being quite simple, 
or without any radiating laminae. 
This 
