Ianthina

Amongst them are prodigious numbers of the ubiquitous violet-coloured _Ianthina_ [2], which rises when the ocean is calm, and by means of its inflated vesicles floats lightly on the surface.

Sketches of the Natural History of Ceylon James Emerson Tennent 1836

The same writer tells us that "a number of little crabs found clinging to the floats of the blue-shelled mollusc, Ianthina, were all coloured of a corresponding blue for concealment." [

Darwinism (1889) Alfred Russel Wallace 1868

On the slightest alarm, the water is discharged, the disc collapses into its original dimensions, and the shell and its inhabitant disappear together beneath the sand.] [Illustration: BULLIA VITTATA] [Footnote 2: _Ianthina communis_, Krause and _I. prolongata_, Blainv.] [Illustration: IANTHINA.]

Sketches of the Natural History of Ceylon James Emerson Tennent 1836

"That shell, Willy," replied Macallan, who, mounting his favourite hobby, immediately spouted his pompous truths, "is called by naturalists the Ianthina fragilis, perhaps the weakest and most delicate in its texture which exists, and yet the _only one_ [see note 1] which ventures to contend with the stormy ocean.

The King's Own Frederick Marryat 1820