30 NAUTILUS. CONUS. 



breeze : two other arms serve as rudders to direct 

 the course. The animal first raises itself to the 

 surface of the sea by ejecting a quantity of water ; 

 if danger occurs, it absorbs water, and thus, by 

 making itself heavier, sinks to the bottom. The 

 species are few in number. 



" Nautilus, pearly sailor, has several charac- 

 teristics of Argonauta ; but the former is con- 

 camerate, the latter without chambers in the shell. 

 The generic characters of Nautilus are, shell 

 univalve, divided into several compartments, 

 communicating with each other by an aperture. 

 Nautilus pompilius is often cut through, or bi- 

 sected, to display the chambers of the shell. In 

 the East, the shells are formed into drinking- 

 cups. Sometimes the outer coat of the shell is 

 removed, and the pearly surface finely carved. 

 This genus, according to Linnasus, consists of 

 fifty-eight species, some of which are fossil. 

 (Plate 6.) 



" In the following genera we must pay particu- 

 lar attention to the aperture of the shell, which 

 is a generic distinction in most univalves. 



" The first is Conus, a large and beautiful 

 genus, including many rare and valuable species. 

 Shell univalve, turbinate, aperture effuse, or 

 having the lips separated by a sinus, linear, 

 without teeth, pillar smooth. In their natural 

 state the shells are usually covered with an epi- 



