72 THE OPEN BOOK OF NATURE 
3. Cephalopoda (Greek, kephale=the head, and 
pous =a foot).—The feet of animals of this class are 
round the head, hence the name. The mouth is sur- 
rounded by tentacles or arms, which bear suckers. 
They breathe by plumelike gills. Examples : Cuttle- 
Uy 
Asiarte Omalit (Pliocene), 
Crassatella sulcata (Eocene). Cardita senilis (Pliocene). 
Fria. 21.—More Fosstn LAMELLIBRANCHS, OR BIVALVES. 
fish and Nautili. Existing species of this class are 
mostly destitute of a shell, although one is possessed 
both by the Paper Nautilus and the Pearly Nautilus. 
Some have an internal skeleton or bone, which in 
some is horny, and in others made of lime. Well- 
developed heads and eyes. The cuttle-fish can swim 
