The Collaborative International Dictionary of English v.0.48:

Staircase \Stair"case`\ (st[^a]r"k[=a]s`), n.
   A flight of stairs with their supporting framework, casing,
   balusters, etc.
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         To make a complete staircase is a curious piece of
         architecture.                            --Sir H.
                                                  Wotton.
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   Staircase shell. (Zool.)
   (a) Any scalaria, or wentletrap.
   (b) Any species of Solarium, or perspective shell.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wentletrap \Wen"tle*trap`\, n. [D. wenteltrap a winding
   staircase; cf. G. wendeltreppe.] [Obs.]
   Any one of numerous species of elegant, usually white, marine
   shells of the genus Scalaria, especially Scalaria pretiosa,
   which was formerly highly valued; -- called also staircase
   shell. See Scalaria.
   [1913 Webster]