2, Flustra abyssicola, M. Sars, 



nov. sp. 

 (PL 2. fig. 2530). 



Of this remarkable deep-water species my Father had already elaborated a full de- 

 scription, which I here quste as exactly as possible from his manuscript. 



The colony is similar to that of F. foliacea, forming an upright leaf-like stem, com- 

 pressed from two sides (see fig. 26) (but less compressed or rather thicker than our other 

 Norwegian species) sometimes undivided, but most frequently scantily branched (fig. 27) na- 

 mely only once or twice bifurcate, with diverging branches all extended in the same, or 

 nearly in the same plane, and gradually becoming much wider towards their extremity, 

 which is truncated, straight, or but slightly curved. The undivided specimens are more linear, 

 or of nearly the s'ame width everywhere, excepting in the top which gradually becomes wider. 

 It is only loosely attached to extraneous bodies which lie at the bottom of the sea (small 

 shells of conchiferae, Rhizopods, grains of sand &c.) by means of numerous very fine soft or 

 membranous cylindrical hyaline root-fibres proceeding from the inferior extremity, and having 

 their extreme points so attached. As it is rigid, not flexible, it is also brittle and easily 

 broken, for which reason perfect specimens are difficult to obtain. The largest specimen found 

 is 32 millimetres high; at the base 1V 2 millimetres wide; higher up 2 2V 2 , and at the end 

 of the branches 5 millimetres wide. The thickness is everywhere the same, a little over Y 2 

 millimetre. Imperfect specimens were also found, the branches of which were 8 millimetres 

 wide at the extremity. 



The cells, which form two parallel layers, attached back to back to each other (one 

 on each of the two broad sides of the colony) are situated in straight longitudinal and oblique 

 transverse rows, or in somewhat irregular quincunx (see fig. 25) as the regular arrangement 

 is here and there interrupted by the intervening (interposite) avicularia, of which more here- 

 after. At the inferior end of the stem there are a few (23) ; at the superior end, or at the 

 extremity of the branches, there may be 8 16 cells in a transverse row. The narrow side- 

 borders of the colony are formed (fig. 26) by two longitudinal rows of cells meeting at an 

 obtuse angle, one row from each of the two broad sides or surfaces. 



The cells are of a membranous or parchment-like quality, of greyish brown color, and 

 tolerably transparent, so that the glassy white animals are clearly seen through them (see 

 fig. 28) about 1 millimetre long and l / 2 millimetre broad, that is larger than in our other 



Norwegian species. Their shape is elongated tongue-like, or similar to that of a bathing 



3* 



