The Collaborative International Dictionary of English v.0.48:

Dextral \Dex"tral\, a. [From Dexter.]
   Right, as opposed to sinistral, or left.
   [1913 Webster]

   Dextral shell (Zool.), a spiral shell the whorls of which
      turn from left right, or like the hands of a watch when
      the apex of the spire is toward the eye of the observer.
      [1913 Webster]