142 CLASS IL— ORDER III. 



ingfor the polypus or constructor of this stony habita- 

 tion. 



Their colour is the same as that of the Corallinas, 

 either fresh or in a dried state. 



They are found on the Thalassiophytes of the va- 

 rious seas, generally on the same species. 



MEMBRANOUS. 



1. Melobesia memhraiiacea. Patches very thin, 

 nearly orbicular ; some projecting cells in the centre, 

 but invisible to the naked eye. 



On the marine plants of the western coast of 

 France. 



PUSTULATED. 



2. Melobesia piistulata. Patches round, and 

 raised as if embossed ; cells visible to the naked eye, 

 and projecting. Plate 12. fig. 2. a. B. 



On the marine plants of the French coast. 



mealy. 



3. MELOBESiA/an«os«. Patches of various shapes, 

 and very thin, in general extremely small, and giving 

 a white dusty appearance to the leaves of the Fu- 

 el ; cells invisible to the naked eye, placed on the 

 summit of small projections. Plate 12. fig. 3. 



Very abundant on the Fucus linifolius. 



WARTY. 



4. Melobesia verruca ta. Patches fragile, with 

 uneven surfaces ; cells placed on the top of small 

 elevations in the form of warts. 



On the Fucus of the Mediterranean. 



