CRISTA DENTICULATA. 4)23 



Zoarium forming large, dense masses, of a stout and erect 

 habit, much branched, punctate; branches straight, 

 broad, flattish, attenuated towards the base, originating 

 from the fourth or fifth cell above the joint, sometimes 

 from the second. Zooecia semialternate, closely aggre- 

 gated, elongate, nearly straight, almost entirely adnate ; 

 orifice elliptical, usually pointed on the outer side above, 

 slightly bent forward, the internodes variable in length, 

 but generally with numerous cells, sometimes as many 

 as 16 or 17; joints usually jet-black. Ocecia oval, sub- 

 pedicellate, thickly speckled, a tubular orifice at the 

 top. 



Height about an inch. 



Var. a. Zoarium more slender; the zooecia much longer, 

 so that the orifices are much more distant from each 

 other longitudinally, and appear less crowded; inter- 

 nodes usually of moderate length. 



C. DENTICULATA is chicfly distinguished by its long, 

 straight, broad and flattened internodes, on which the 

 cells are closely packed together. In habit it is de- 

 cidedly stout and erect. 



Habitat. In clefts and rock-pools near low-water mark, 

 and on Algse and zoophytes &c. from tide-marks to deep 

 water. 



Localities. Very generally distributed. 



Geographical Distribution, Roscolf, on rocks, and 

 especially on Cystoseira fibrosa (Joliet) : Adriatic 

 (Heller) : Madeira ; South Africa (Busk) : Norway, 30- 

 100 fathoms (Sars) : Bahusia; Spitzbergen (Smitt) : Kara 

 sea (Stuxberg & Theel) : Grand Manau, 10 fathoms 

 (Stimpson) . 



Range in Time. Lower Suffolk Crag; Palaeolithic (A. 

 Bell) : Scotch Glacial deposits (Geikie) . 



