Definify.com
Webster 1913 Edition
Testaceous
1.
Of or pertaining to shells; consisted of a hard shell, or having a hard shell.
2.
(Bot. & Zool.)
Having a dull red brick color or a brownish yellow color.
Testaceous animals
(Zool.)
, animals having a firm, calcareous shell, as oysters and clams, thus distinguished from
crustaceous animals
, whose shells are more thin and soft, and consist of several joints, or articulations, as lobsters and crabs.