ESCHARID^ : CELLULARIA. 339 



PLATE LXIII. FIG. 7, 8. 



Bird's-head Coralline, Ellis Corall. 36, no. 2, pi. 20, fig. a. ^.Cellularia avicularia, 

 Pall. Blench. 68. Johns. Brit. Zooph. 292, pi. 36, fig. 7, 8. Couch Zooph. Corn. 



58 : Corn. Faun. iii. 128. Van Beneden Recherch. 41 and 48, pi. 6, fig. 1-8 



Sertularia avicularia, Lin. Syst. 1315. Berk. Syn. i. 220. Cellaria avicularia. 

 Ellis and Soland. Zooph. 22. Lam. An. s. Vert. 2de. dit. ii. 191. Johnston in 

 Trans. Newc. Soc. ii. 262. Crisia avicularia, Lamour. Cor. Flex. 141. Templeton 

 in Mag. Nat. Hist. ix. 468. Cellularia avicularis, Reid in Ann. and Mag. Nat. 

 Hist. xvi. 389. 



Hob. Parasitical on other corallines in deep water. 



Polypidom caulescent, erect, bushy, from one to two inches in 

 height, membrano-calcareous, silvery or glassy greyish-white, brittle 

 when dry, attached by a fibrous root, the stalk composed of numerous 

 interwoven fibres ; primary branches alternate, flabellate, divided 

 dichotomously into many narrow linear flat segments, which are 

 rough and cellular on the upper or inner side, but smooth and lon- 

 gitudinally striate underneath. Cells in two semialternating rows, 

 coalescent, opening on one plane, oblong, flat, their parietes thin and 

 pellucid, a strong spine at each of the superior angles, the aperture 

 subterminal, transverse, generally covered with a large globular 

 pearly operculum placed between the spines ; and at the external 

 side there is in many a curious appendage which Ellis has aptly 

 compared to a "bird's head, with a crooked beak, opening very 

 wide." These appendages, of unknown use, are about one fourth the 

 size of the cell, and, when the coralline is in a living state, are con- 

 tinually moved upwards and downwards with the regularity of a 

 pendulum. The polypes have apparently twelve tentacula. 



Many naturalists make this zoophyte a variety of Flustra avicu- 

 laris, but Mr. Bean and Milne Edwards dissent from the association. 

 The principal distinction between them lies in the dissimilarity of 

 their habit : in the shape of the cells I do not perceive any notice- 

 able difference. "It can, however, be readily distinguished from 

 the latter (Flustra avicularis) by all the branches being composed of 

 two rows of semi-alternate cells, and each cell having only two 

 conical spines directed upwards or in the line of the long axis of the 

 cells, and a little outwards and forwards, and attached to the angles 

 of the superior margin of the cell. In a small number of cells an 

 additional small spine, making three in all, projected from the outer 

 angle in the same direction as the normal one. On the other hand, 

 almost all the cells in Flustra avicularis have four spines, which 

 differ in appearance from those of Cellularia avicularis. This spe- 



z 2 



