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]