242 NATURAL HISTOEY OF 



" The cells are broadly elliptical or hexagonal, with 

 generally two hollow tubercles on the posterior angle 

 of the aperture/' Landshorough. 



7. M. LiNEATA, Linn. Plate XX. fig. 2. 



Flustra lineata {Linn., Fabr., Mull., Lamx., Jameson, 

 Le B., G. J., D. L), Callopora lineata {Gray), Eepte- 

 lectrina lineata {D'Orb.). 



Hab. : Common on rocks, shells, and seaweed. 



This species spreads in irregularly circular patches. 

 The cells are oval, protected by 6 — 12 spines, most of 

 which bend across the cell so as almost to meet. The 

 ovicels are large and pearly, and generally accompanied 

 by an avicularium. 



8. M. CEATicuLA, Alder. 

 Flustra lineata {R. Q.G.). 



Hab. : Eare. Northumberland {Aid.), Isle of Man, 

 Oban {T.K), Wick, Cornwall {G. W.P.). 



The cells are oval and regularly arranged. Each cell 

 is protected by about 13 closely-set, glistening spines, 

 the two upper ones being of great length. 



9. M. spiNiPERA, Johnston. 

 Flustra spinifera {G. J.). 



Hab. : Northumberland and Durham {Aid.), Isle of 

 Man, Devon {T. E.), St. Andrews {McL). 



This species is distinguished from M. lineata by its 

 numerous long stout spines (14 — 18), and its stalked 

 avicularium. 



10. M. PLUSTROiDES, Rinchs. 



Hab. : Guernsey, Cornwall, South Devon {T. H.), 

 Birterbay Bay {Norman). 



Described by Mr. Hincks in the Annals of N. H., 

 ser. 4, XX. 213. 



Mr. Hincks considers this species as transitional 



