16 



Thoa Halecina, Lmiouroux's Cor. Flex., p. 211. Johnston's 

 Brit. Zooph., p. 119, pi. 6. 



Hab. On stones and shells, especially the Pinna Ingeus, 

 from deep water west of the EJdystone to Falmouth ; 

 com mon. 



This species grows to the height of eleven inches, and from 

 four to eleven inches in breadth. In young specimens, the 

 polypidom is of a ligbt horn colour, which in the older turns 

 to a dark brown. The polypidom is arborescent, much 

 branched, and rooted by numerous fibres interwoven and 

 matted with each other. The trunk is formed of numerous 

 sub-parallel tubes agglutinated together. The branches are 

 brown, and when dry very brittle; they are irregularly 

 given off; the pinnas are alternate, and both erecto-patent. 

 Here for the first time the polypes have cells, into which 

 they can retire for shelter; they do not, however afford 

 such complete shelter as in the following genera. The cells 

 are alternate, tubular, bi-articulate and with plain apertures. 

 The Ovarian vesicles are scattered over every part of the 

 polypidom, but are most abundant about the axillae, of the 

 pinnee; they are pedunculated, smooth, with a long neeks and 

 edges round them like a jug. 



T. MURICATA. Very rigid, irregularly branched, bran- 

 ches semi-erect and spreading; cells alternate, visible on 

 the younger branches only ; vesicle small, round, and 

 prickly, cup shaped, with an even aperture, separated from 

 the stem by a joint. 



Sertularia Muricata, Ellis and Solander's Zooph., p. 59, 

 pi. 7, figs. 3 and 4. Turton's Lin., vol. 4, p. 681. Stewart's 

 Elem., vol. 2, p. 445. Laomedea Muricata, Lamouroux's 

 Cor. Flex., p. 209. Thoa Muricata, Johnston's Brit. Zooph., 

 p. 121, pi. vii., figs. 3, 4. 



Hab. On a shell from deep water, off Mevagissey ; rare. 



This rare and stout species rises from a fibrous and spongy 

 hase to the height of three inches. It is very stiff, irregu- 

 larly branched, of alight dull brown colour, and is composed 

 of a great number of small tubes very irregularly twisted on 

 each other. The branches are numerous, irregular tubular. 

 The cells are minute and frequently absent, being destroyed 

 by the action of the sea. The vesicles are clustered, round 

 and beset with prickles. 



SERTULARIA, Linnaeus. 

 Generis Character: Polypidoms rooted, plant-like, variously 

 branched, divisions or branches formed of a single tube, 

 divided at regular intervals by imperfect septa; cells 

 paired of arranged in two opposite rows, sessile, distinct 



