Webster's Revised Unabridged Dictionary · 1913

Malacostraca

Malacostraca , proper noun, plural

[New Latin, from Greek malako`s soft + {not transcribed} shell of a testacean.]

(Zoology) A subclass of Crustacea, including Arthrostraca and Thoracostraca, or all those higher than the Entomostraca.