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 



Fig. 45. 





The Pearly Nautilus (Nautilus pompilius). 



«, body ; h, 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 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. 



