nau·ti·lus /ˈnɔtḷəs, ˈnɑ-/
 鸚鵡螺,缸魚,鸚鵡螺號
 Nau·ti·lus n.; pl. E. Nautiluses L. Nautili
 1. Zool. 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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 nautilus
      n 1: a submarine that is propelled by nuclear power [syn: nuclear
           submarine, nuclear-powered submarine]
      2: cephalopod mollusk of warm seas whose females have delicate
         papery spiral shells [syn: paper nautilus, Argonaut, Argonauta
         argo]
      3: cephalopod of the Indian and Pacific oceans having a spiral
         shell with pale pearly partitions [syn: chambered
         nautilus, pearly nautilus]
      [also: nautili (pl)]