332 HISTORY OF BRITISH ZOOPHYTES. 



2. MEMBRANIPORA MEMBRANACEA, Dr. Fleming. 



Hab. " Common, especially on stones near low-water 

 mark/' Dr. Fleming. " I have never seen it on seaweeds," 

 Dr. Johnston. On the coast of Ayrshire it is common on 

 the inside surface of old specimens of Buccinum undatum ; 

 I have it also on the outside of Patella carulea, 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 lie 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 carulea ? Even 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- 



