CABEREA BORYI. 61 



length, and opens below into a deep channelled space, 

 inclosed at each side by a prolongation of the cell-walls, 

 which tapers off downwards and is carried along the 

 median line until it reaches the wall of the next vibra- 

 cular cell. Owing to this arrangement of the vibracula, 

 a very large proportion of the dorsal surface of the zoa- 

 rium is covered by them. 



A striking feature of the present species is the remark- 

 able development of the radical fibres, and the mode in 

 which they are disposed. They take their origin on the 

 side of the vibracular cells, and are given off from the 

 upper as well as from the lower portion of the branches. 

 Passing off from the vibracula on each side of the zoarium, 

 the tubes tend downwards along the median line of the 

 dorsal surface, one superimposed upon the other, and all 

 closely adherent, so as to form in the adult colony a 

 prominent keel-like projection along the back of the 

 branches. As growth proceeds and new cells are formed 

 fresh strands are added to the fibrous bundle, which is, 

 of course, smallest above. Below each bifurcation the 

 bundles join and blend, while at the base of the zoarium 

 the multitudinous threads become free and form so many 

 separate cables by which the polyzoon is anchored in 

 its place. 



All the fibres are carried down the centre of the dorsal 

 surface, and neatly piled up along the median line: so 

 that there is no interference with the action of the 

 vibracula. 



Caberea Boryi, Audouin. 



PlateVIII. figs. 9-11. 



Crista Eoryi, Auchuin, Espl. : Savigny, Egypte, pi. xii. fig. 4. 

 Cellularia Hookeri, Fleming, B. A. 539. 

 Selbia zelanica, Gray, DiefTenbach's New Zeal. ii. 292. 

 Caberea ZELANicA, .Bws/?.-, Voy. ' Hattlesuake/ i, 378. 



