tes·ta·cea \teˈstāsh(ē)ə\noun plural Usage: capitalized Etymology: New Latin, from Latin, neuter plural of testaceus covered with a shell : an order of Rhizopoda containing forms (as of the genera Arcella and Difflugia) with an external test • tes·ta·cean\(ˈ) ̷ ̷| ̷ ̷shən\adjective or noun