119 
of alternating approximated cells; cells oval, horizontal, 
membranous; the apertures patulous, with hard calcareous 
rims. Polypes ascidian. 
Hairy SEA-MAT. M. Pilosa. Aperture of the cells 
oval, armed with horizontal teeth pointing towards the 
centre, and with one long bristle on the proximal margin. 
Plustra pilosa, Ellis and Solander’s Zooph., p. 13. Ir- 
re gular spongy foliaceous coralline, Ellis’ Coral., p. 73, 
Pi. 31. F. pilosa, Turton’s Lin., vol. 4, p. 663. Stewart’s 
Elem., vol. 2, p. 436. Fleming’s Brit. An., p. 537. Tem- 
pleton in Mag. Nat. Hist., vol. 9, p.469. Johnston’s Brit. 
^°oph., p. 280, pi. 34. 
There is a variety of this species, in which the long 
bristle is either not formed, or destroyed, and is described 
by the following authors as a distinct species. 
Ellis Coral,, pi. 29, fig. D. Flustra dentata, Ellis and 
Solander’s Zooph., p. 15. Turton’s Lin., vol. 4. p, 664. 
Stewart’s Elem., vol. 2, p. 436. TeinpleLon in Mag. Nat. 
Hist., vol. 9, p. 469. 
Sab. On stones, shells, and especially fuci about low 
'rater mark; abundant. 
This is found under a great variety of appearances, de- 
pending on the nature and form of the substance on which 
j* grows. It is encrusting; the cells are ova), slightly 
mbular, membrano-calcareous with thickened rims. The 
a Pertures which are oval, are guarded by horizontal teeth 
Pointing towards the centre. In the most perfect specimens, 
oere is a long slender bristle on the proximal lip ; this how- 
e 'er is sometimes absent, but there is generally a sufficient 
remnant to show its previous existence. As it grows on the 
Pollute fuci about low water mark, the cells are frequently 
.^visible from the length and prominency of these bristles ; 
pence the polypidoms look very hairy. The absence of the 
ristle is generally found in specimens which grow on tho 
r °ods of tlie larger fuci. This has given rise to the sup- 
P° s jtion that there are two species; but there are generally 
Efficient traces left behind to prove their destruction. As 
Y' le . ^ ar ger sea-weeds are liable to continued, and frequently 
^ lu lent motion, the delicate and friable appendages are easily 
a . < j str °yed ; whereas on the smaller fuci, which are stiff and 
Sl 0vv of hut of little motion, these parts are generally in a 
af at e of perfection. Specimens are sometimes found which 
ti t) ° Ver y dissimilar in appearance, and in tact look like dis- 
di s pecies, but after examining numerous specimens, no 
g ' nct ive differences can be detected between them, and 
p ra at ‘°ns can be traced into each other, so that for the 
sent they must be consided as one species. 
