138 MOLLUSCA. 
DIADEMA, Ranz., 
Where the tubular portion is almost spherical, and which has 
but two small valves hidden in the membrane which closes the 
operculum. ‘The opercular valves would not effectually close 
the orifice without the membrane which unites them. 
They also live on the balenz, and otiones are frequently ob- 
served attached to their surface. (Lepas Diadema, Chemn. 
VIII. xcix. 848, 844.) 
ae 
