TRITONIA. 119 
GENUS TRITONIA. 
The body is prismatic ; that is to say, lengthened 
with ridges or angles running along it; it is often 
thick and firm. There are two tentacles, consisting 
of several branched filaments arranged in the form 
of a bundle or brush, and capable of being with- 
drawn into tubular sheaths. The head is protected 
by a veil sometimes cleft into filaments. The gills 
are small branching plumes, arranged in a single 
series along a ridge bordering each side of the 
back. 
The largest British species of the whole Order 
is a member of this genus, Zritonia Hombergi, 
TRITONIA HOMBERGI. 
which grows to six inches or more in length. It 
varies considerably in colour, being generally of a 
pink or purple hue, often varied with blue, but 
sometimes the entire animal is of an amber 
yellow. 
This very fine species occurs all round our coast, 
