They appear especially common in the sea near Australia; and off Cape Leeuwin I found an allied, but smaller and apparently different species.

Captain Cook, in his third voyage, remarks that the sailors gave to this appearance the name of sea-sawdust.
Near Keeling Atoll, in the Indian Ocean, I observed many little masses of confervae a few inches square, consisting of long cylindrical threads of excessive thinness, so as to be barely visible to the naked eye, mingled with other rather larger bodies, finely conical at both ends.

Two of these are shown in Plate 6 united together.

They vary in length from .04 to .06, and even to .08 of an inch in length; and in diameter from .006 to .008 of an inch.

Near one extremity of the cylindrical part, a green septum, formed of granular matter, and thickest in the middle, may generally be seen.