The Collaborative International Dictionary of English v.0.48:

Scalaria \Sca*la"ri*a\, n. [L., flight of steps.] (Zool.)
   Any one of numerous species of marine gastropods of the genus
   Scalaria, or family Scalaridae, having elongated spiral
   turreted shells, with rounded whorls, usually crossed by ribs
   or varices. The color is generally white or pale. Called also
   ladder shell, and wentletrap. See Ptenoglossa, and
   Wentletrap.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ladder \Lad"der\ (l[a^]d"d[~e]r), n. [OE. laddre, AS.
   hl[=ae]der, hl[=ae]dder; akin to OFries. hladder, OHG.
   leitara, G. leiter, and from the root of E. lean, v.
   [root]40. See Lean, v. i., and cf. Climax.]
   1. A frame usually portable, of wood, metal, or rope, for
      ascent and descent, consisting of two side pieces to which
      are fastened cross strips or rounds forming steps.
      [1913 Webster]

            Some the engines play,
            And some, more bold, mount ladders to the fire.
                                                  --Dryden.
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   2. That which resembles a ladder in form or use; hence, that
      by means of which one attains to eminence; as, to climb
      the corporate ladder.
      [1913 Webster +PJC]

            Lowliness is young ambition's ladder. --Shak.
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   Fish ladder. See under Fish.

   Ladder beetle (Zool.), an American leaf beetle (Chrysomela
      scalaris). The elytra are silvery white, striped and
      spotted with green; the under wings are rose-colored. It
      feeds upon the linden tree.

   Ladder handle, an iron rail at the side of a vertical fixed
      ladder, to grasp with the hand in climbing.

   Ladder shell (Zool.), a spiral marine shell of the genus
      Scalaria. See Scalaria.
      [1913 Webster]