from the GNU version of the Collaborative International Dictionary of English
- n.pl. 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.
from The Century Dictionary and Cyclopedia
- A division of gastropods, usually held as an order or a suborder of Gastropoda, which have a single lateral gill, covered by the mantle (whence the name), and whose shell, varying in size according to the genus, is very small and sometimes concealed.
Sorry, no etymologies found.