174 



GENUS I. ACTINIA (Linn.). 



Entacmaa (Ehrenberg). 



Base adhering to rocks ; considerably exceeding 

 diameter of column. 



Column pillar-shaped, usually much wider than 

 high ; margin greatly developed, smooth, separated by 

 a broad, but shallow fosse from the outer tentacles ; a 

 circle of vividly coloured spherules projecting from 

 the inner surface of the wall of the fosse ; surface 

 delicately smooth, imperforate, non-adhesive ; sub- 

 stance fleshy. 



Disk greatly expanded and overarching ; concave. 



Tentacles in several rows ; moderately long ; nearly 

 equal ; unicolorous ; wholly retractile. 



Mouth set on a protrusile cone ; two pairs of goni- 

 dial tubercles, brightly coloured. 



We possess but a single British species, A. mesem- 



bryantliemam. 



