Page:Natural History, Mollusca.djvu/34 the thinnest glass. They
possess a pair of large membranous fins, which closely resemble
the wings of a butterfly, and by using these organs in a
flapping manner, the little animals swim briskly about. Perhaps
some of my readers will expect me to include the beautiful Paper
Nautilus (Argonauta), among swimming Mollusks; seeing that the
poets have claimed for it the honour of teaching navigation to
man:— "Learn of the little Nautilus to sail, Montgomery, the
poet of the ocean, thus beautifully expresses the popular
notions concerning it:—