152 CONCHOLOGIST’S COMPANION, 
that name in the Linnzan system, and is denomi- 
nated Argonauta, from a favourite companion of Jason, 
in the celebrated voyage of the ship Argo. The art 
of navigation is supposed to have owed its origin to 
the expert management of this instinctive sailor, as 
well as to that of the Nautilus. Like the latter, he 
frequently rises to the surface of the sea, by ejecting 
a quantity of water, and thus diminishing the specific 
gravity of his shell; nay, more, he guides his mimic 
vessel by means of several oar-shaped tentacule, and 
also expands a little membrane which answers the 
purpose of a sail. These, on the approach of danger 
are immediately lowered down, and by a rapid ab- 
sorption of water, the Argonauta descends into the 
deep. A fact, thus accurately noticed and described 
by Pliny :— 
** One of the greatest wonders in creation is a certain 
shell-fish, called by some the Nautilus, and by others 
Pompilus. When this extraordinary creature wishes 
to rise above the water, he turns upon his back, 
raises himself by little and little, and in order to 
swim with greater facility, throws out all the water 
contained in his shell. His body being thus lightened, 
he lifts up his two foremost claws, or arms, and 
stretches out between them a fine membrane. This 
serves him for a sail above water, and with his other 
he works his way beneath it, directing his course with 
