teleobranchia

from The Century Dictionary.

• A group of rostriferous gastropods, with the gills of few (12 to 15) laminæ in regular descending spiral rows on the left side of the mantle-cavity, the operculum distinct, and the aperture of the shell contracted moderately and roundish. It includes the families Planaxidæ, Rissoidæ, Melaniidæ, Cerithiidæ, Viriparidæ, and others.