166 MEMBRANIPORID^. 



Membranipora Rosselii, Audouin. 



Plate XXII. fig. 4. 



Flustra Rosselii, Aud. Expl. 240: Savigny, Egypte, pi. x. fig. 11. 

 Membranipok.4. Eosselii, Busk, B.M. Cat. ii. 59, pi. c. fig. 2 : Hincks, 



Devon Cat. 38 {se^.): Heller, Bryoz. Ad. Meer. 20: "iManzoni, 



I.e., Contr. 4, 11, pi. iii. fig. 15. 



Zooscia oval, or elongate, v/ide and arched above, con- 

 tracted below, and either truncate or pointed at the 

 lower extremity, very regularly quincuncial ; a minutely 

 granulated lamina filling in more than half the area ; 

 aperture longer than broad, arched above, widest below, 

 and contracted towards the top, lower margin straight 

 or slightly curved inwards ; margin of the cell much 

 raised, especially above the aperture, finely beaded. 

 Ooecia flattened in front. Avicularia none. 



Colonies forming very flat, closely appressed, neat-looking 

 brownish crusts, often of large size. 



Range of Variation. There are considerable differences 

 in the shape of the zooecium, which is sometimes pretty 

 regularly oval ; but more commonly it exhibits a rudely 

 lozenge-shaped figure, elongate, and rather narrow in 

 proportion to its length, arched above, where it is widest, 

 contracting from about the middle downwards, and termi- 

 nating below in a truncate or pointed extremity. The 

 margin is generally more elevated above the aperture 

 than elsewhere, and sometimes forms a very thick and 

 prominent wall at this point. The aperture usually occu- 

 pies decidedly less than half the area, but in some cases 

 a rather larger proportion. 



Habitat. On shells (chiefly) and stones, from shallow 

 to deep water. 



Localities. Orkney (Busk) : Shetland, on stones, 

 Outer Haaf, 80-140 fathoms (A. M. N.) : Isle of Man, 

 ofl' Maughold Head; Torbay, forming large patches on 



