70 
ROOM XI. 
Nat. Hist. 
Most of the animals of this Class form a coral 
covering into which they can withdraw themselves 
from external danger. This coral is calcareous, and the 
cells which are inhabited by the animals are furnished 
with more or less distinct longitudinal lamellae, placed in 
a radiating position round the central axis, so as to give 
the cavity a star-like appearance. The corals are-gene¬ 
rally attached to marine bodies during the whole of their 
growth. Some few kinds, as the Sea Mushroom 
(. Fungia ), and the Sea Slug (Polyphyllia), are attached 
when they are young by a short stem, but the crown 
separates from the stem by a natural absorption as the 
coral enlarges, leaving it at length quite free. 
The reefs and islands, which are constantly forming 
in certain seas, especially the Pacific Ocean, are the 
work of the minute animals which inhabit these kinds 
of coral. 
Corals, on account of the different forms which they 
present, have been divided into several genera, easily 
separated into groups by the manner in which their 
cells are placed with reference to each other. 
In the first of these groups the cells are simple and 
separate, having a regular circumscribed edge, over 
which the internal laminae are often inflected, as in the 
Sea Mushrooms (Fungia and Cyclolithes ), both of which 
are expanded and hemispherical. The Turbinoliae 
( Turbinolid) and Caryophyllioe ( Caryopliyllia) re¬ 
semble these in many particulars, but they differ in being 
of a conical or cylindrical shape : the former of these, 
like the Fungise,- becomes free by age, while the latter 
is always attached. 
The second group only differs from the former by 
the cell springing from a ramose base, the branches 
ending in simple stars : these, in their young state, are 
scarcely to be distinguished, except by their cylindrical 
form, from the Caryophylliae. In one of these (Dendro- 
phylla) the stars are simple; in the other ( Lobcphylla ) 
they are irregular, and the laminae of which the stars 
are formed are irregular and jagged. 
In 
