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GENUS 1. ACTINIA (Linn.). 
Entacmcea (Ehrenbebg). 
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. 
Dish 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- 
bryantliemum. 
