Flustra. 
Z. ASCIDIOIDA. 
289 
Flustra hispida, Fabric. Faun. Groenl. 438 Jameson in Wern. Mem. J. 
563. Flem. Brit. Anim. 537. Johnston in Trans. Newc. Soc. ii. 266, 
pi. 9, fig. 7 La F; hispide, Blainv. Actinolog. 450. 
Hab. “ 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 different species, it has become necessary to adopt 
another specific name. 
11. F. tuberculata, membrano-calcareous ; cells oval with 
two short spines at the sides of the aperture and one above it. 
Fleming. 
Plate xxxiv. Fig- 9. 
Flustra tuberculata? Bose , Vers, iii. 143 <c F. dentata? Mull. Zook 
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. FI. membranacea? Lam. Anim. s. Vert. 2de edit. ii. 225. Le 
Membranipore unicorne? Blainv. Actinolog. 447 La Flustre uni- 
corne, Ibid. 450. 
Hab. On stones within low water-mark, 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 0 
a), but in old or exposed specimens no vestige of them can be disco- 
vered. (Fig. b.) 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 Muller’s figure, 
but the description of F. tuberculata given by Bose 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 
