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CLASS I.— ORDER I. 



GENERA AND SPECIES. 



CELLEPORA. 



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 arc distinguished by the form and si- 

 tuation of the opening of their cells, which we may 



