18 MOLLUSCA. 
air. While it remains dry, it will float the animal, 
which then glides along as if on a solid body, 
crawling, in fact, on the inferior surface of the avr: 
put if by any agitation of the water, or by the will 
of the animal, the foot become overflowed, the state 
of suspension is ended, and the creature falls to the 
POULPE AND CALAMARY, 
bottom. The Pond-snails (Zumneus), with olive- 
coloured fragile shells, that inhabit every little 
pool and lakelet, may be seen in a summer’s day, 
by scores, enjoying the air in this manner. 
The wide ocean between the tropics is inhabited 
