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Nautilus

Nautilus.jpg A Grazing Bison, Delicately and Carefully Drawn, Engraved on a Wall of the Altamira Cave, Northern SpainThumbnailsThe walking-fish or mud-skipper (Periophthalmus)A Grazing Bison, Delicately and Carefully Drawn, Engraved on a Wall of the Altamira Cave, Northern SpainThumbnailsThe walking-fish or mud-skipper (Periophthalmus)A Grazing Bison, Delicately and Carefully Drawn, Engraved on a Wall of the Altamira Cave, Northern SpainThumbnailsThe walking-fish or mud-skipper (Periophthalmus)

A section through the Pearly Nautilus, Nautilus pompilius, common from Malay to Fiji. The shell is often about 9 inches long. The animal lives in the last chamber only, but a tube (S) runs through the empty chambers, perforating the partitions (SE). The bulk of the animal is marked VM; the eye is shown at E; a hood is marked H; round the mouth there are numerous lobes (L) bearing protrusible tentacles, some of which are shown. When the animal is swimming near the surface the tentacles radiate out in all directions, and it has been described as "a shell with something like a cauliflower sticking out of it." The Pearly Nautilus is a good example of a conservative type, for it began in the Triassic Era. But the family of Nautiloids to which it belongs illustrates very vividly what is meant by a dwindling race. The Nautiloids began in the Cambrian, reached their golden age in the Silurian, and began to decline markedly in the Carboniferous. There are 2,500 extinct or fossil species of Nautiloids, and only 4 living to-day.

Author
The Project Gutenberg EBook of The Outline of Science, Vol. 1 (of 4), by J. Arthur Thomson
Published in 1922
Available from gutenberg.org
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