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. ? avicularxa, 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. Elench. 68. Hogg's Stock. 35 Sertularia avicu- 
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. Bose, Vers, iii. 131. Lam. Anim. s. Vert. ii. 141. 
2de edit. ii. 191. Johnston in Trans. Newc. Soc. ii. 262 Crisia 
avicularia, Lamour. Cor. Flex. 141. Corail. 61. Templeton, in Mag. 
Nat. Hist. ix. 468- 
Hah. 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 Eean. 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 
