The location and basic structures of the gills of
the agnathan hagfishes and lampreys, elasmobranchs,
and teleosts are illustrated in Fig. 1. In
all fishes, the gills are bilaterally situated on either
side of the pharynx and are composed of a series of
pouch-like or arch-like structures that provide the
physical support for the delicate gill filaments also
termed primary lamellae.