The genera Preptetos Pritchard, 1960 and Neopreptetos Machida, 1982 are redefined. The following species are described and/or recorded from marine fishes. From the Great Barrier Reef: Preptetos caballeroi Pritchard, 1960 in Naso annula-tus, N. brevirnslris and N. vlamingii·, P. xesuri (Yamaguti, 1940) in Zebrasoma veliferum and Z. scopas; Preptetos cannoni Barker, Bray et Cribb, 1993 in Siganus dolialus and S. fuscescens', Preptetos laguncula sp. n. in Naso unicornis (type-host); P. impar sp. n. in Lutjanus erythropterus (type-host) and L. malabaricus·, Neopreptetos arusettae Machida, 1982 in Pomacanthus semicirculatus·, and N. kurochkini (Toman, 1989) in Chaetodontoplus meredithi. From southwestern Australia: Preptetos rotto sp. n. in Nelusetta ayraudi (type-host), Neosebastes pandus, Oplegnathus woodwardi and Pagrus auratus. The new combination Preptetos trulla (Linton, 1907) (originally Distomum then Lepocreadium) is made and the species Lepocreadium areolatum (Linton, 1900) is considered likely to belong in Preptetos.
The bathymetric range of 149 digenean species recorded deeper than 200 m, the approximate depth of the continental shelf/slope break, are presented in graphical form. It is found that only representatives of the four families Lepocreadiidae, Fellodistomidae, Derogenidae and Hemiuridae reach to abyssal regions (>4,000 m). Three other families, the Lecithasteridae, Zoogonidae and Opecoelidae, have truly deep-water forms reaching deeper than 3,000 m. Bathymetric data are available for the Acanthocolpidae, Accacoeliidae, Bucephalidae, Cryptogonimidae, Faustulidae, Gorgoderidae, Monorchiidae and Sanguinicolidae showing that they reach deeper than 200 m. No bathymetric data are available for the members of the Bivesiculidae and Hirudinellidae which are reported from deep-sea hosts. These results indicate that only seventeen out of the 150 or so digenean families are reported in the deep sea.