22 MOLLUSCA. 
exeel 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), 
PAPER NAUTILUS. 
among swimming Mollusks; seeing that the poets 
have claimed for it the honour of teaching navi- 
gation to man :— 
“Learn of the little Nautilus to sail, 
Spread the thin oar, and catch the rising gale.”—PopE. 
Montgomery, the poet of the ocean, thus beauti- 
fully expresses the popular notions concerning 
it:— 
