Tectibranchiata
Tectibranchiata , noun, plural
[New Latin, from Latin tectus (past participle of tegere to cover) + Greek {not transcribed} a gill.]
(Zoology) An order, or suborder, of gastropod Mollusca in which the gills are usually situated on one side of the back, and protected by a fold of the mantle. When there is a shell, it is usually thin and delicate and often rudimentary. The aplysias and the bubble shells are examples.