Ill, 



mnit^aibt^. 



SHELLS OF ONE PART ONLY, AND HAVING A REGULAR 

 SPIRE, 



NAUTA.— Paper Sailor. 



Animal — a Sepia or Clio: Shell univalve, spiral^ invo- 

 lutef membranaceouSy one-celled. 



THE genus Argonauta contains but five species; and, in 

 so small a number, much variety is not to be expected. 



The form throughout is generally like that of a scroll, 

 with a very large aperture, and mostly a double carinated 

 outer margin. However, in the Argonauta Vitrea (the 

 Glassy Nautilus) the margin is but single : this rare and 

 beautiful species is by far the most costly of any. 



The shells of this genus are remarkable for their exces- 

 sive thinness, brittleness, and lightness. The Argonauta 

 Argo, usually known by the name of the Paper Nautilus, 

 is the identical shell supposed in the early ages of society 

 to have first taught men the use of sails. When it intends 

 to sail, it discharges a quantity of water, by which it was 

 made heavier than the sea-water, and rising to the sur- 



