Primnoa. ZOOPHYTA. CORALLINADiE. 513 



Gen. XXXIII. PRIMNOA.— -Cells subpedunculated pendu- 

 lous. The axis, when young, is corneous, but in the older 

 branches it becomes like bone. The flesh is covered with 

 minute fixed scales. The cells are crowded, bell-shaped, 

 and with the aperture, according to Baster, closed by two 

 valves, covered with imbricated moveable scales. The 

 branches are dichotomous. M. Lamouroux, who first se- 

 parated this genus from Gorgonia, considers the pendulous 

 cells as the polypi themselves. 



77. P. lepadifera. 



Gorgonia lep. Bast. sp. 11. 130. t. xiii. f. J. Ellis, Zoop. p. 84. tab. xiii. 

 f. 1, 2. 



This species, which is common on the Norwegian coast, has been found, 

 according to Professor Jameson (Wern. Mem. i. p. 560.), at Zetland and 

 Aberdeenshire. 



CORALLINAD^E. 



The objects of this group, forming the genus Corallina of Linnseus, 

 are usually plant-like or branched, and consist of two substances, a 

 central corneous axis, and an external calcareous crust. The axis is 

 sometimes fleshy, and shrinks by drying, leaving a tubular cavity. The 

 substance is fibrous, and united with the exterior crust. This last is 

 hard, studded on the surface with minute marginated pores, and usually 

 covering the axis in an irregularly interrupted manner, giving the body 

 3, jointed appearance. When the calcareous matter is removed by a 

 weak acid, a granular-looking skeleton remains, the granules appearing 

 to be united with the extremities of the fibres which proceed from the 

 axis, and seem to be the remains of the polypi. Reproduction appears 

 to take place by means of enlargements or processes, on the sides, or 

 at the extremities, forming hollow cells, chiefly derived from the corti- 

 cal layer. Ellis observes, " That we may perceive the pores or cells 

 of this class the more distinctly, it is necessary they should be viewed 

 immediately upon being taken out of the sea ; for, as they dry, the cre- 

 taceous or coralline matter shrinks, and unites the pore-like cells on 

 the surface, scarcely to be distinguished from a polished superficies, 

 without the help of the very best glasses." All the species reside in 

 shallow water, in places accessible at low water of spring-tides. 



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