THE FLAXEN FLUSTRA. 93 



inhabited by a polyp, which extends at will its 

 ciliated arms. 



The Flustra carba- 

 cea or flaxen flustra, is 

 found on shells from 

 deep water on the 

 southern coast, on that 

 of Durham, on Leith 

 shore, and on the coast 

 of Ireland. It is fixed 

 by a small disc, nar- 

 row at the base, with 

 thickened margins di- 

 lating upwards, and 

 becoming very broad 

 in proportion to the 

 height, which at most 

 is about two inches ; 

 it is thin, yellowish 

 brown, deeply divided, ^r*unmu. PLUSTHA CAKBACEA. 



and the segments are broad, and somewhat rounded 

 at the apex. 



The cells on one side are large and smooth, the 

 polyps have about twenty-two arms, which are 

 nearly one-third of the length of the body, and 

 there appear to be about fifty cilia on each side of 

 an arm, making 22,000 cilia on each polyp. In this 

 species, there are more than eighteen cells in a 

 square line, and 1,800 in a square inch of surface, 

 and as the branches of an ordinary specimen 



