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. 



Flustra pilosa, Ellis and Solander's Zooph., p. 13. Ir- 

 regular 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. 

 Zooph., 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. Tern pie ton in Mag. Nat. 

 Hist, vol. 9, p. 469. 



Ilab. On stones, shells, and especially fuci about low 

 water mark ; abundant. 



This is found under a great variety of appearances, de- 

 pending on the nature and form of the substance on which 

 it grows. It is encrusting; the cells are ova!, slightly 

 tubular, mem bran o-calcareous with thickened rims. The 

 apertures which are oval, are guarded by horizontal teeth 

 pointing towards the centre. In the most perfect specimens, 

 there is a long slender bristle on the proximal Jip ; this how- 

 ever is sometimes absent, but there is generally a sufficient 

 remnant to show its previous existence. As it grows on the 

 minute fuci about low water mark, the cells are frequently 

 invisible from the length and prominency of these bristles ; 

 hence the polypidoms look very hairy. The absence of the 

 bristle is generally found in specimens which grow on the 

 fronds of the larger fuci. This has given rise to the sup- 

 position that there are two species ; but there are generally 

 sufficient traces left behind to prove their destruction. As 

 the larger sea-weeds are liable to continued, and frequently 

 violent motion, the delicate and friable appendages are easily 

 destroyed ; whereas on the smaller fuci, which are stiff and 

 allow of but of little motion, these parts are generally in a 

 state of perfection. Specimens are sometimes found which 

 are very dissimilar in appearance, anti in fact look like dis- 

 tinct species, but after examining numerous specimens, no 

 distinctive differences can be detected between then?, and 

 gradations can be traced into each other, so that lor the 

 present they must be consideU as one species. 



