The tegument of the adult form of Prosorhynchoides arcuatus
(Linton, 1900) (Trematoda, Bucephalidae) from the
intestine of Pomatomus saltator (L.) from the Atlantic
coast of the State of Rio de Janeiro, Brazil was studied by
transmission electron microscopy. The tegument consists of
two layers: an external, constituted by a syncytium,
containing spines, unicilliated papillae, inclusion bodies and
mitochondria and an internal, consisting of a muscular layer
and mononucleated tegumental cells.