FLUSTRAD^E. 



FAMILY IV. BICELLARIAD^. 



15 



Bicellaria (De Bl.). Cells top-shaped, distinct, 

 armed with spines ; aperture looking upwards. 



B. ciliata. Fig. 21 ; n.s. and mag. 

 Bugula (Oken). Cells elliptical, closely con- 

 tiguous, in two or more rows ; aperture very 

 large ; margin simple, not thickened ; birds'-heads 

 (generally present) stalked and jointed. 



B. neritina. B. plumosa. 



flabellata. Murrayana. 



avicularia. Fig. 22 ; n. s. and ; 



FAMILY V. FLUSTRAD^. 



Flustra (Linn.). Cells contiguous, on both sides 

 of the expansion. 



F. foliacea. F. truncata. 



papyracea. Fig. 23 ; n. s. and mag. 



Carbasea (Gray). Cells contiguous, on one side 

 only. 



C. papyrea. Fig. 24 ; n. s. and mag. 



