292 Z. ASCIDIOIDA. Cellularia. 



The radical tubes are flexuous, corneous, and divided at the extremity 

 into two or three small knob-like processes. Branches linear, plane, 

 jointed at their origins, composed of two rows of semialternate oval 

 cells, with an oblique terminal aperture level with the surface, and 

 armed with several short brittle spines. Ellis represents only two 

 spines to each cell, and Pallas follows him in his description, but they 

 are commonly more numerous. Stretched across the mouth of the 

 cells there may occasionally be observed, in dried specimens, an ir- 

 regularly veined pellucid membrane, undoubtedly the remains of the 

 polype's sac or tunic. Opercula are also to be seen over some cells, 

 but these are not common. 



4. C. ? AvicuLARiA, erect^ dichotomous ; the cells with two 



spines at the aperture. Ellis. 



Plate xxxvi. Fig. 7, 8. 

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



avicularia. Pall. Eleiich. 68. Hogg's Stock. 35. Sertularia a\'icu- 



laria, Lin. Syst. 1315. Berk. Syn. i. 220. Wern. Mem. i. 565. Turt. 



Brit. Faun. 216. Stew. Elem. ii. 448. Cellaria avicularia, Ellis and 



Soland. Zooph. 22. ^osc, Vers, iii. 131. Lam. Anim. s. Vert ii. 141. 



2de edit. ii. 191. Johnston in Trans. Newc. See. ii. 262 Crisia 



avicularia, Lamoiir. Cor. Flex. 141. Corall. 61. Templeton, in Mag. 

 Nat. Hist. ix. 468. 

 Hab. Parasitical on other corallines in deep water. From the 

 sea-coast near Dublin, Ellis. " Mare inter Angliam et continen- 

 tem terram," Pallas. Not very uncommon at Hartlepool, J. Hogg. 

 Leith shore, not common, Jameson. Scarborough, on stones &c. 

 at low water, not uncommon, Mr Bean. Ireland, Templeton. 



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

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

 tle when dry, attached by a fibrous root, the stalk composed of nu- 

 merous interwoven fibres ; primary branches alternate, flabellate, di- 

 vided dichotomously into many narrow linear flat segments, which 

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

 longitudinally 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 com- 

 pared 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 continually 



