124 HISTORY OF BRITISH ZOOPHYTES. 
Hab. On shells, and roots of Fuci, and not unfrequently 
with us on the branches of Halidrys. It is common at 
Troon, and at other places on the Ayrshire coast. I have a 
specimen from Newfoundland. 
It is loosely branched, cells smooth, not crowded, in some 
specimens a little wrinkled across. It is white, and two or 
three inches high. 
There are two varieties, the one upright, and the other 
more branched and spreading. 
“When this coralline was put into sea-water, I observed, 
through the microscope, a polype occupy the inside of the 
whole, and each denticle or cell filled with a part of it, end- 
ing in tufts of tentacula. A small piece of one of the little 
sprigs was put into a watch-glass of sea-water, and notwith- 
standing the separation of its body, in five minutes’ time 
the claws or tentacula were moving about in search of prey.” 
—Hils. 
2. SerTuLARIA RuUGOoSA, Snail Trefoil Coralline, v/s. 
(Plate IV. fig. 11.) 
Hab. Parasitical on Plustre, sponges, and seaweeds at 
low-water mark; not uncommon. ‘There is a variety which 
is erect, and another variety which creeps along the frond 
of Flustra foliacea. Seen by the naked eye, it has no beauty, 
