218 MICHOPOIIELLID.^. 



tributed over the zoarium. In this variety too the surface 

 is either smooth or minutely granulated, like shagreen. 



L. plugiopora, Busk, from the Crag, should j)robably 

 be ranked as a variety of the present species. It differs 

 from it in the size and oblique direction of the avicula- 

 rium — points which taken by themselves are of very small 

 moment. 



Smitt has suggested that if from any cause the avicu- 

 larium were more fully developed than usual, as not 

 unfrequently happens in other species, it might probably 

 take an oblique direction to obtain sufficient space. 



In a beautiful specimen from the Crag (Plate XXX. 

 fig. 4) each cell is bounded by an incised line, within 

 which is a roAV of numerous small punctures, which are 

 occasionally channelled. 



M. violacea is commonly of a dark purplish colour; 

 but cream-coloured specimens not unfrequently occur. 

 Heller remarks that the light-coloured form is pretty 

 common in the Adriatic, but that he had ouly observed 

 the dark violet variety once. 



Habitat. On shells, stones, Nullipores, &c., generally 

 in moderate depths. 



Localities. Isle of Man (E. Forbes) : Cornwall (Peach) : 

 Brixhani, from the trawlers ; Torbay ; off the Deadman ; 

 Guernsey (T. H.) : Birterbuy Bay (G. S. Brady). 



Var. a. Guernsey, abundant (T. H.) : Hastings (Miss 

 Jelly) . 



Geographical Distribution. Roscoff, extreme low- 

 water mark (Joliet) : Algiers (J. Y. J.) : Adriatic, the 

 light-coloured variety pretty common, the dark violet once 

 on Nullipore (Heller) : Gibraltar Bay (Landsborough) : 

 Mazatlan, on Murex and Byssoarca pacifica ; Adelaide, a 

 much thickened variety (T. H.) : west off Tortugas, in 

 35 fathoms (Pourtales) : Charente-Inferieurc (Fischer). 



