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:

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]