1  definition  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Nautilus  \Nau"ti*lus\,  n.;  pl  E.  {Nautiluses},  L.  {Nautili}. 
  [L.,  fr  gr  nayti`los  a  seaman,  sailor,  a  kind  of  shellfish 
  which  was  supposed  to  be  furnished  with  a  membrane  which 
  served  as  a  sail;  fr  nay^s  ship.  See  {Nave}  of  a  church.] 
  1.  (Zo["o]l.)  The  only  existing  genus  of  tetrabranchiate 
  cephalopods.  About  four  species  are  found  living  in  the 
  tropical  Pacific,  but  many  other  species  are  found  fossil. 
  The  shell  is  spiral,  symmetrical,  and  chambered,  or 
  divided  into  several  cavities  by  simple  curved  partitions, 
  which  are  traversed  and  connected  together  by  a  continuous 
  and  nearly  central  tube  or  siphuncle.  See 
  {Tetrabranchiata}. 
 
  Note:  The  head  of  the  animal  bears  numerous  simple  tapered 
  arms,  or  tentacles,  arranged  in  groups,  but  not 
  furnished  with  suckers.  The  siphon,  unlike,  that  of 
  ordinary  cephalopods,  is  not  a  closed  tube,  and  is  not 
  used  as  a  locomotive  organ,  but  merely  serves  to 
  conduct  water  to  and  from  the  gill  cavity,  which 
  contains  two  pairs  of  gills.  The  animal  occupies  only 
  the  outer  chamber  of  the  shell;  the  others  are  filled 
  with  gas.  It  creeps  over  the  bottom  of  the  sea,  not 
  coming  to  the  surface  to  swim  or  sail,  as  was  formerly 
  imagined. 
 
  2.  The  argonaut;  --  also  called  {paper  nautilus}.  See 
  {Argonauta},  and  {Paper  nautilus},  under  {Paper}. 
 
  3.  A  variety  of  diving  bell,  the  lateral  as  well  as  vertical 
  motions  of  which  are  controlled,  by  the  occupants. 

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