The colouring matter which they emit has no stinging, electric or deleterious properties whatever, that I could discover.  I found that when this colouring matter was mixed with water, it became of a deep blue.  In those which I caught in November 1837, I may have been deceived, and the colouring matter might also possibly have been scarlet directly it was emitted.  It is difficult to conceive what use this liquid can be to the fish against its foes, yet it certainly uses it as a means of defence.

To one of these shells, the fish in which was alive and well, we found attached a number of barnacles, some of which were of large size.

This sort of Janthina was very abundant; today we caught eight, and saw great numbers of them:  yesterday we caught a smaller one of a different species. (Janthina exigua.)

This kind of Janthina is attached to its float by a sort of peduncle, which it has the power of elongating, so that the fish itself sinks, with its shell, and yet remains attached to the float, which continues at the surface.  In one instance, I saw this peduncle elongated to a length of 0.9 inches.  It may, of course, have the power of sinking itself much lower than I have seen it do.  When it is in this state, the apparatus with which it fills the float remains behind the peduncle in a state of perfect quiescence.

The scarlet fluid emitted by this animal is of such a consistency that it can be drawn away from it out of the water, like a glutinous thread.

A part of the animal requires attention, it is composed of an outer cup, or circular lip, which it has the power of contracting or expanding in the same manner as the valve; and when opened out like a cup, an orifice can be seen at the bottom of it.  It can also expand, and make broad the arm; and it then appears to use them as sails.

This species of Janthina, I afterwards found, has the power of in some manner taking in by suction a quantity of water, which it can suddenly expel again with great violence, sending it out as if from a squirt.

We caught, also, an extraordinary fish this day.  Its mouth has the appearance of being situated on its back; a fin, 0.4 inches in length, projected directly out from one side of the fish, and there was every appearance of a perfectly similar one having been torn from the other side; a hard horny membrane projected from underneath the stomach of the animal, being apparently a sort of fin.

Its colour was of a silvery metallic lustre, having in parts a burnished appearance, except where it is shaded (see Illustration 5 and below) and then it was of a dark green colour; the tail was perfectly transparent, except just where it joined the body, and there, where the shaded line is, it was dark green.

This fish was swimming about, apparently preying on the tentaculae of the barnacles, of which there were numbers round the ship attached to the dead Velella, some of which I had caught yesterday; it appears therefore probable that its mouth was placed in so extraordinary a position to enable it to seize this pendant prey.