History of British animals - University of Guam Marine Laboratory

Primnoa. ZOOPHYTA. CORALLINADiE. 513Gen. XXXIII. PRIMNOA.—-Cells subpedunculated pendulous.The axis, when young, is corneous, but in the olderbranches it becomes like bone. The flesh is covered withminute fixed scales. The cells are crowded, bell-shaped,and with the aperture, according to Baster, closed by twovalves, covered with imbricated moveable scales. Thebranches are dichotomous. M. Lamouroux, who first separatedthis genus from Gorgonia, considers the pendulouscells as the polypithemselves.77. P. lepadifera.Gorgonia lep. Bast. sp. 11. 130. t. xiii. f. J. Ellis, Zoop. p.f. 1, 2.84. tab. xiii.This species, which is common on the Norwegian coast, has been found,according to Professor Jameson (Wern. Mem. i. p. 560.), at Zetland andAberdeenshire.CORALLINAD^E.The objectsof this group, forming the genusCorallina of Linnseus,are usually plant-likeor branched, and consist of two substances, acentral corneous axis, and an external calcareous crust. The axis issometimes fleshy, and shrinks by drying, leaving a tubular cavity.Thesubstance is fibrous, and united with the exterior crust. This last ishard, studded on the surface with minute marginated pores, and usuallycovering the axis in an irregularly interrupted manner, giving the body3, jointed appearance.When the calcareous matter is removed by aweak acid, a granular-looking skeleton remains, the granules appearingto be united with the extremities of the fibres which proceed from theaxis, and seem to be the remains of the polypi.Reproduction appearsto take place by means of enlargements or processes, on the sides, orat the extremities, forming hollow cells, chiefly derived from the corticallayer.Ellis observes, " That we may perceivethe pores or cellsof this class the more distinctly,it is necessary they should be viewedimmediately upon being taken out of the sea ; for, as they dry,the cretaceousor coralline matter shrinks, and unites the pore-like cells onthe surface, scarcelyto be distinguished from a polished superficies,without the help of the very best glasses."All the species reside inshallow water, in places accessible at low water of spring-tides.vol. r.k k