50 SHELL GALLERY. 
number of small retractile feelers. The Nautilus occasionally swims, 
like other members of its class, at the surface of the sea, but mostly 
The Pearly Nautilus (Nautilus pompilius). 
a, body ; b, siphuncle ; c, eye ; d, hood ; e, tentacles ; /, muscle of 
attachment to the shell ; g, siphon. 
crawls about leisurely on its feet at the bottom in search of food, 
which consists chiefly of small crabs or Mollusca, which it crushes 
with its strong calcareous parrot-like mandibles. 
The chambered shell is pearly within, and covered with an ex- 
ternal calcareous layer. The chambers are connected by a slender 
tube or siphon, the function of which is not at present thoroughly 
understood. The septa, or partitions across the shell, indicate periods 
of growth. When the Nautilus outgrows the capacity of the outer 
chamber, in which it resides, it constructs a new one of larger size, 
separating the additional chamber from the preceding one by a 
transverse partition. 
A series of Cephalopods preserved in spirit is exhibited in the 
black upright case at the side of the room. 
