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is well known that the common Cuttle Fish, and other living species of Cephalopods, which have no external shell, are protected from their enemies by a peculiar internal provision, consisting of a bladder-shaped sac, containing a black and viscid ink, the ejection of which defends them, by rendering opaque the water in which they thus become concealed. The most familiar examples of this contrivance are found in the Sepia vulgaris, and Loligo of our own seas. (See Pl. 28, Fig. 1.)

It was hardly to be expected that we should find, amid the petrified remains of animals of the ancient world, (remains which have been buried for countless centuries in the deep foundations of the earth,) traces of so delicate a fluid as the ink which was contained within the bodies of extinct species of Cephalopods, that perished at periods so incalculably remote; yet the preservation of this substance is established

and marine shells, with the exception of the Argonaut, Nautilus, Ianthina, Lithodomus, Haliotis, and great radiated crystalline Teredo from the East Indies, exceeded Carara marble in density. This marble and the Haliotis are of equal specific gravities."—De la Beche's Geological Researches, 1834, p. 76.