44 CLASS I.— ORDER I. 



that surround his mouth, he gives a rotatory motion 

 to the water, and involves in this diminutive whirlpool 

 the animals on which he feeds. 



The color of the Flustra is in general a lighter or 

 a darker fawn ; sometimes they incline to red, or grey ; 

 but they never assume those brilliant hues which are 

 seen in the Corallines and Sertularias. 



Left to themselves and without support, I know no 

 species that exceeds two decimetres in height ; but at- 

 tached to the leaves, or surrounding the branches of 

 the great Thalassiophytes, they envelop these in a 

 cretaceous covering, which sometimes extends itself 

 over the whole plant. 



The Flustras are found in all seas, and in all depths, 

 on the marine plants of the deepest waters, as well as 

 on those that are scattered on our shores ; in the 

 neighbourhood of the polar ices, as well as under the 

 burning sun of the tropics. 



The seas of former periods enclosed them in their 

 bosoms, as well as the Cellepores ; and their impres- 

 sions, or their fragments, are discovered in those cal- 

 careous rocks that are anterior to chalk formations. 



FOLIACEOUS OR LEAFY. 



1. Flustra foUacea, Branching ; divisions fan 

 and other shapes. 



Seas of Europe. 



TRUNCATED. 



2. Flustra truncata. Leaf-like and dichotomous ; 

 divisions linear and truncated. 



Seas of Europe. 



