SERTULARIA. 125 



seeming like a brown thread somehow attached, but when 

 viewed with a lens it is a great curiosity, for it is crowded 

 with coarsely wrinkled cells like little barrels. The vesicles 

 are much the same, but larger, and have three teeth in the 

 opening at the top of each. 



** Cells in pairs, opposite, alternate. 



3. SERTTJLARIA ROSACEA, Lily or Pomegranate Coralline, 

 Ellis. (Plate IV. fig. 12.) 



Hab. On shells from deep water, and also on Laminarice, 

 but much more frequently on Plumulariafalcata, Sertularia 

 argentea, and S. cupressina, and on these it is much more 

 delicate and graceful than on seaweeds. 



It is from one to two inches in height, very slender and 

 delicate, of a pale horn-colour, pellucid ; cells opposite, tu- 

 bulous, the upper half free and divergent. Ellis saw the 

 animals alive both in the cells and in the vesicles, those in 

 the vesicles being considerably larger. 



4. SERTULARIA PUMILA, Sea-oak Coralline, S. Doody. 

 (Plate IV. fig. 13.) 



Hab. Near low-water mark; very common on Fucus nodo- 

 sus and Fucus serratus. The branches rise from a tubular 

 thread that creeps along the surface of the Fuci, and they 

 often rise in such numbers as to cover the alga. In general 



