A revision of Heterocotyle (Monogenea:Monocotylidae) with a description of Heterocotyle capricornensis n. sp.  from Himantura fai (Dasyatididae) from Heron Island, Great Barrier Reef, Australia. 
Heterocotyle capricornensis n. sp.  is described from the gills of Himantura fai collected from Heron Island, Great Barrier Reef, Australia.  It is distinguished from other species in the genus by the morphology of the sclerotised male copulatory organ which is curved and tapered distally, the ovary which loops once before entering the oviduct, and the testis which has 3 posteriorly-directed lobes.  The oncomiracidium of this species is also described.  The homology between glands found in the oncomiracidium and the adult is discussed.  Additional data based on the examination of type material and, in some cases, new material of previously described species are included.  The genus is revised and a key to species is provided.  Characters which unite the members of the genus could not be confirmed for Heterocotyle elliptica Pillai & Pillai, 1976 and H. robusta (Johnston & Tiegs, 1992) Price, 1938 and therefore we consider them species inquirendae.  New host and locality records are presented for H. chinensis Timofeeva, 1983 and a new host record is presented for H. granulatae Young, 1967.  Host-specificity and phylogenetic relationships in Heterocotyle are discussed.