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. SERTULARIA RrosACEA, Lily or Pomegranate Coralline, 
Ellis. (Plate LV. fig. 12.) 
Hab. On shells from deep water, and also on Laminaria, 
but much more frequently on Plumularia falcata, 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. 18.) 
Hab. Near low-water mark; very common on Pueus nodo- 
sus and Pucus 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 
