MEMBRANIPORA LINEATA. 143 



Membranipora hexagonAj Busk. 

 Plate XVIII. fig. 7. 



Membranipora hexagona, BusJc, Quart. Joum. Micr. Sc, Zoophytology, iv. 



308, pi. xii. fig. 4. 

 FiiUSTRA coriacea, Johist. B. Z. ed. 2, 348 (tlie diagnosis by Forbes), pi. Ivi. 



fig. 8. 



Zooecia hexagoual or subelliptical ; surface smooth ; mar- 

 gin smooth and ev^en ; mouth semilunar. 



Habitat. On shells and stones. 



Localities. Isle of Man^ on Pecten opercularis (E. 

 Forbes) : coast of Devon (Miss Cutler) . 



Mr. Busk is probably correct in identifying E. Forbes's 

 Flustra coriacea Avith the present species. 



I know nothing of M. hexagona but what may be 

 gathered from the brief description and figure in the 

 ' Zoophytology.^ 



Judging from the figure^ the covering of the area is 

 wholly membranous^ and the zoarium appears to form a 

 thin flat crust. 



Membranipora lineata, Linnseus. 

 Plate XIX. figs. 3-6. 



Flustra lineata, Linn. Syst. ed. 12, 1301 : Fabr. Faun. Groeiil. 437: Johnst. 

 B. Z. ed. 2, 349, ?pl. Ixvi. fig. 4*. 



* There is much difficulty in determining the synonymy of this and the 

 allied spiniferous forms, as the descriptions of authors are often extremely 

 vague, and have probably in many cases been based on specimens of more 

 than one species. 



Johnston's figure of his F. lineata is useless as a means of identification. 



