Source : Webster's Revised Unabridged Dictionary (1913)

Slit-shell \Slit"-shell"\, n. (Zo["o]l.)
   Any species of {Pleurotomaria}, a genus of beautiful, pearly,
   spiral gastropod shells having a deep slit in the outer lip.
   Many fossil species are known, and a few living ones are
   found in deep water in tropical seas.