CRisiA. 283 



Mr. Hassall describes it as follows : — " Cells disposed in 

 a double series, armed with a long spinous process ; joints 

 of an amber-colour; vesicles much resembling a fig in 

 shape, and dotted/^ Mr. W. W. Saunders says that it is 

 not uncommon at Brighton and Hastings; but he consi- 

 ders it as the perfect state of Crisia ehurnea. 



4. Crisia geniculata, /. /. Lister. 



Hab. On littoral algse, Brighton, Lister; on Ri/tiphlcea 

 pinastroides, Brighton, W. W. Saunders; Strangford Lough, 

 W. Thompson; Ayrshire coast, D. L. 



Dr. Johnston states that this differs from Crisia ehurnea 

 in being more slender and less calcareous ; — in the straight- 

 ness of the secondary branches, and in the tubular form of 

 the cells, which are alternate and free at the apices. I do 

 not thini: that the specific name given it by Milne Edwards 

 is very characteristic, for, as Dr. Johnston states, it is only 

 subgeniculate. He thinks that the characters which dis- 

 tinguish it from C. ehurnea are rather those of a variety 

 than of a species. I have sometimes thought so too ; and 

 yet I am, on the whole, disposed to regard it as distinct. 

 On the A}Tsliire coast C. ehurnea is found on almost every- 

 thing, whereas C. geniculata is scarcely ever seen except 

 on Besmarestia aculeata, which is often quite hoary with 



