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CLASS I.— ORDER I. 
GENERA AND SPECIES. 
CELLEPOEA. 
Polypidoms partly membranous; in stony con- 
crete expansions, or subfoliated: very fragile, and 
furnished on their external surface with urceolated, 
or else turban-shaped projecting cells. 
The Celleporas are not remarkable either in form or 
colour ; they often escape observation, appearing like 
simple calcareous concretions, from their minuteness, 
or rendered less visible by their half transparency. 
Their polypi are not sufficiently known to admit 
a description ; the rapidity of their movements ren- 
ders the difficulty of observing them very great. 
These polypidoms are usually found in patches 
of greater or less expansion, on all marine produc- 
tions, whether vegetable or solid ; they exist in all seas 
and in all depths. 
Their species are distinguished by the form and si- 
tuation of the opening of their cells, which we may 
