external gill(n = noun.animal) - occurs in some mollusks and in tadpoles and other immature amphibians;
is a kind of branchia, gill

abdominal external oblique muscle, external, external angle, external auditory canal, external body part, external carotid, external carotid artery, external drive, external ear, external iliac artery, external iliac vein, external jugular vein, external maxillary artery, external nasal vein, external oblique muscle, external organ, external orifice, external respiration, external storage, gill, gill arch, gill bar, gill cleft, gill fungus, gill net, gill slit