Neotropical Monogenoidea. 31. Ancyrocephalinae (Dactylogyridae) of piranha and their relatives (Teleostei, Serrasalmidae) from Brazil: species of Notothecium Boeger and Kritsky, 1988, and Enallothecium gen. n. Journal of the Helminthological Society of Washington, 65(1), January 1998: 31-49. 41 [Zoological Record Volume 136]