130 Beautiful Shells. 
The True, or Pearly Nautilus (N. Pompilius), 
the origin of whose specific name we have been 
unable to discover, is much like the Argonaut in 
appearance and general construction ; the shell is 
externally smoother and more iridescent, it is also 
generally somewhat thicker than the former kind, 
and has internally more chambers or divisions; its 
pearly lustre renders it a beautiful ornament, and 
the large size it frequently attains a very con- 

spicuous one. Its inhabitant has several pecn- 
liarities of organization, which distinguish it from 
the Argonauts, but into these we need not enter ; 
neither can we pause to describe the other species 
of Nautili, the shells of which, like those of the 
Cowry and other univalves, are covered with a 
membrane which hides their beauty. ‘This mem- 
brane or mantle sometimes extends some distance 
beyond the edge of the shell, and, being of a light 
and filmy appearance, may have been mistaken for 
a sail hoisted by the creature to catch the breeze, 
