The frontal cells are situated at the apex of the gill filament.
The surface of these cells is covered by many individual cilia.
These bands of frontal cilia run the length of the gill filament
to the food groove. The frontal ciliary
tracts serve to conduct captured food particles to the food groove,
and from thence to the labial palps and the mouth.
Images of frontal cilia are below.
1.
An SEM of the gill of Polymesoda caroliniana showing the
frontal cilia running from left to right in the image. The structures
that resemble horse tails are the frontal
cirri typical of this species. Also note that they are all
on the same side of each gill filament. Approx. magnification
of the original photo - 1.03kx.