420 CRISIIDiE. 



geniculata of Milne-Edwards as a variety of the present 

 species ; indeed I have met with what seems to be a form 

 or condition of C. cornuta which agrees with it in most 

 respects. But if the two are identical^ the distinguished 

 French zoologist must have overlooked the jointed cha- 

 racter of the zoarium^ which is neither mentioned in his 

 description nor shown in his figure. The regularity with 

 which the zooecia in C. geniculata are bent alternately in 

 opposite directions^ so as to give the stems a zigzagged 

 appearance^ has no parallel in the usual form of C. cornuta ; 

 but a similar arrangement occurs in the variety setacea of 

 Couch. In the ordinary condition the cells are in a single 

 line and all turned one way. 



Habitat. On Algse^ zoophytes^ surface of rocks, shells, 

 &c., from tide-marks to deep water. 



Localities. Widely distributed. Cornwall (Couch) : 

 Scilly ; Mount's Bay ; South Devon ; Swanage ; Ilfra- 

 combe ; Llandudno ; Isle of Man ; Filey ; Oban (T. II.) : 

 Durham, south coast, common (J. Hogg) : Wick and 

 Peterhead (C. W. P.) : Cullcrcoats (Alder) : Shetland, 

 tide-marks (A. M. N.), &c. 



Var. With the cells inclined alternately to opposite sides. 

 Ilfracombe, on the underside of rocks (T. H.). 



Geographical Distribution. Roscoff, on Algae and 

 various marine bodies at all depths (Joliet) : Mediterranean 

 (Pallas) : Bahusia (Lov^n) : Norway (Sars). 



b. With the cells in two series. 

 Crisia eburnea, Linnaeus. 



Plate LVI. figs. 5, B. Woodcut, fig. 21. 



"Tufted Ivory Ooralline," Ellis, Corall. 39, no. 6, pi. xxi. fig. a A. 

 Sertulakia eburnea, Linn. cd. 12, 1.310 : Jameson, Mem. Wern. Soc. i. .50.5 

 (1809). 



