THE CEPHALOUS MOLLUSKS. 227 
delicate; its head ornamented in front with a starry veil, fine as 
gauze, and surmounted by two long horns, as transparent as glass, 
the extremity of which opens into a bouquet of pink branches 
mingled with violet flowers. Next to the tritons rank the 
Scyllea. 
The Scylle@a pelagica is well known; it is found on the sea- 
weeds of all parts of the world. It has a flat body, and clings 
to the aquatic plants with its narrow, hollow foot. Its respiratory 
organs are upon its back, rising like two membranous crests, 
which run parallel to each other, and from whose interior surfaces 
spring hair-like filaments; the mouth widens out like a trumpet, 
and, to conclude this complicated organism, the stomach possesses 
a fleshy ring, armed with horny plates which are as sharp as knives. 
Forster has described, under the name of G/aucus, a gasteropod 
of the same kind, yet somewhat different from the scyllaea. The 
elauci, according to his description, are elegant little swimmers ; 
their long, gelatinous bodies are contracted towards their posterior, 
and terminate in a grey, pointed tail, like that of the salamander. 
Their colour is a pearly grey, which shades off into sky-blue ; 
their back is covered with nacre, and two bands of the sky- 
blue pass along its whole length. Their under surface is brown. 
They possess but a small head, which is furnished with four 
conical horns, or feelers, arranged in pairs. On each side of 
the body are swimming organs—oval, fan-like fins—whose purple 
colour contrasts pleasingly with the rest of the body of this gay 
little mollusk. Each of the fans is a broad plate, fringed with 
minute, flexible points. The posterior ones, for there are two on 
each side, gradually thin away until their projection loses itself 
in the tail. The animal when at rest is always lying on its back. 
It is not fond of moving, but when it does it swims with rapidity, 
and is as much distinguished for the elegance of its motion as 
for the beauty of its colouring. 
Cuvier gave the name of Eolis to some naked gasteropods 
which are also remarkable. The great naturalist described them 
as little Limaces without either mantle or shell. Their head 
carries four feelers, and their mouth is fringed with tentacles. 
Their respiratory organs are placed in bunches of filaments upon 
the back—not on the ridge of the back, but some way down the 
1 
