joe HISTORY OF BRITISH ZOOPHYTES. 
2. MEMBRANIPORA MEMBRANACEA, Dr. Fleming. 
Hab. “Common, especially on stones near low-water 
mark,” Dr. Fleming. ‘TI have never seen it on seaweeds,” 
Dr. Johnston. On the coast of Ayrshire it is common on 
the inside surface of old specimens of Buccinuwm undatum ; 
I have it also on the outside of Patella caerulea, D. L. 
This is the Flustra unicornis of Dr. Fleming; the Flustra 
tuberculata of Dr. Johnston’s first edition. It spreads to a 
considerable extent as a thin gauze-like crust of a whitish 
‘colour. The cells have a large ovate aperture, and above 
it there is a stout hollow conical process. 
The workmanship is very delicate, and He who made the 
artificer endowed it with instinctive prudence to choose a 
sheltered position for its domicile. It spreads itself on the 
smooth pure white inner surface of a newly deserted Bucci- 
num, and though the shell should be tumbled about with the 
storm, the inside colony are perfectly safe. But where is the 
prudence, it may be said, in building its city on the very out- 
side summit of Patella caerulea? Fiven here its prudence 
is not at fault, for the Patella chooses for itself one of 
the snuggest possible residences. It hollows out a cave in 
which it may ensconce itself in the very centre of the roots 
of Laminaria digitata, and in this munition the Membrani- 
