Definition of zoothecium in English:
zoothecium
nounˌzuːə(ʊ)ˈθiːsɪəmˌzəʊə(ʊ)ˈθiːsɪəm
rare An aggregate of the fused shells or protective sheaths of certain aquatic colonial protozoans.
Origin
Late 19th century; earliest use found in William Saville-Kent (1845–1908), marine biologist.