Flustra. Z. yVSCIDIOIDA. 289 



Flustra liisi)ida, Fabric. Faun. Groenl. 438 Jameson in Wern. Mem. ''. 

 563. Flem. Brit. Anim. 537- Johnston in Trans. Newc. Soc. ii. '260, 



pi. 9, fig. 7 La F. hispide, Blainv. Actinolog. 450. 



Hub. " Investing- Fucus serratus ; everywhere common," Flem- 

 ing. Leith shore, Jameson. Berwick Bay, at low water mark. 



" Substance thick, tough, full of mucus, brown ; base of the cells, 

 where attached, contiguous and angular ; at the surface the cells are 

 ovate, the aperture lunate. Polypi with an enlarged head, and from 

 20 to 30 tentacula," Fleming. — As the Flustra hispida of Pallas is 

 unquestionably a diffex'ent species, it has become necessary to adopt 

 another specific name. 



1 1. F. TUBERCULATA, membrano-colcareoiis ; cells oval with 

 tioo short spines at the sides of the aperture and one above it. 



Fleming. 



Plate xxxiv. Fig. 9. 

 Flustra tiiberculata ? Bosc, Vers, iii. 143 " F. dentata ? Mull. Zoo). 



Dan. iii. tab. 95, fig. 1, 2." F. unicornis? Fleming, in Edin. Phil. 



Journ. ii. 87. Flem. Brit. Anim. 536. Johnston, in Trans. Newc. Soc. 



ii. 266. Fl. membranacea? Lam. Anim. s. Vert. 2de edit. ii. 225. Le 



Membranipore unicorne? Blainv. Actinolog. 447 La Flustre uni- 



come, Ibid. 450. 

 Hah. On stones within low water-mai'k, Fleming. Frequent in 

 Berwick Bay. 



Polypidom in the form of a thin closely adherent greyish- white 

 subcalcareous crust, reticulated like a piece of gauze to the naked eye, 

 spreading circularly : cells quincuncial, short, oval, with a large ovate 

 aperture armed with two short spinous teeth inclined inwards, the 

 margin somewhat thickened : in the space between the cells and 

 above the aperture there is a conical process which appears to be per- 

 forated on the top. 



This is more calcareous in its texture than any of the preceding- 

 species, and hence assumes a white colour when dried. When per- 

 fect and young, the denticles to the aperture are very evident, (Fig. 

 a), but in old or exposed specimens no vestige of them can be disco- 

 vered. (Fig. h.) At one time I had nearly concluded that these 

 specimens belonged to different species, but the timely possession of 

 a perfect polypidom prevented the commission of the error, for in it 

 the cells towards the margin have all the characters of a, and those 

 near the centre the character of b. I have not seen MuUer's figure, 

 but the description of F. tuberculata given by Bosc agrees with the 

 the first state of the species ; and it appears to be probable that on 

 the second state is founded the F. unicornis of Fleming. 



T 



