Thecosonlata

Thecosonlata, the order of Pteropoda (q.v.) which includes those members of this class in which the body is protected by a mantle fold and a shell. It includes three living families, of which the Hyaleidae is the best known; the two Palaeozoic families of Conularidae and Theciidae are included here, but it is doubtful whether these are really Pteropods.