BICELLARIA ALDERI. 71 



laterally, often disjunct, turbinate, much produced and 

 attenuated downwards; dorsal surface smooth and en- 

 tire; aperture broad above, with a somewhat straight 

 upper margin, narrowed below, occupying usually less 

 than half the length of the cell, bearing a single, very 

 long, curved spine on its outer angle. Avicularia capi- 

 tate, much swollen, placed on the side of the cells at 

 the lower extremity, with the mandible directed out- 

 wards. Oce.cia superior, subglobose; surface entire, 

 polished, marked with fine radiating striae. 

 Po/ypide with. 16 to 18 tentacles. Primary cell small, very 

 slender and cylindrical below, with an elliptical aperture 

 bearing on its margin six outspread spines. 



Habitat. On hydroids (especially), Gorgonia, small stones, 

 and shells from deep water. 



Localities. Shetland (Barlee) : 5 to 7 miles east of the 

 island of Balta in 40-70 fathoms on soft ground; off 

 Unst and Out Skerries, in 40-100 fathoms (A. M. N.). 



Geographical Distribution. OEsterraat, Norway, at- 

 tached to small stones and shells in 80-100 fathoms (M. 

 Sars) : otf the coast of Norway in 200 fathoms (Baron 

 Uggla) : the Bommel-Fjord, 106 fathoms (Kircheupauer). 



In this delicate and graceful species the two lines of cells 

 which compose the shoots are not welded together so as 

 to form one solid piece, but ratlier run side by side united 

 at certain points and more or less separated through a great 

 portion of their length. They are very loosely connected, 

 and at the extremity of the shoots are usually altogether 

 disjunct. The condition of the zoarium in this respect marks 

 the transition from the simply uniserial forms to those in 

 which the series of cells are more thoroughly connate, 

 such as Cellularia, &c. In the present species the shoots 

 commence with a few single cells^ which rise one from the 

 other, each taking its origin above the angle which is 



