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GENUS V. ARACHNACTIS (Sars). 
Column moderately long, cylindrical, rounded at 
the inferior extremity, but not swollen, imperforate. 
Surface capable of temporary adhesion, and therefore 
probably studded with minute suckers. 
Bisk ? 
Tentacles of two kinds, the one marginal, very long, 
slender ; the other gular, short ; few in each series, not 
retractile. 
Mouth, a simple slit. 
Habit: freely swimming in the sea. 
There is but one British species, A. albida. 
