The Collaborative International Dictionary of English v.0.48:

Ostreaceous \Os`tre*a"ceous\, a. [L. ostrea an oyster. See
   Oyster.] (Zool.)
   Of or pertaining to an oyster, or to a shell; shelly.
   [1913 Webster]

         The crustaceous or ostreaceous body.     --Cudworth.
   [1913 Webster]