NEOTROPICAL MONOGENOIDEA .29. ANCYROCEPHALINAE (DACTYLOGYRIDAE) OF PIRANHA AND THEIR RELATIVES (TELEOSTEI, SERRASALMIDAE) FROM BRAZIL - SPECIES OF AMPHITHECIUM BOEGER AND KRITSKY, 1988, HETEROTHECIUM GEN-N ANDPITHANOTHECIUM GEN-N

Fifteen species (9 new) of Amphithecium, 2 new species of Heterotheciu m, and 2 species of Pithanothecium are described and/or reported from the gills of 14 species of Serrasalmidae from the Brazilian Amazon: Am phithecium calycinum Boeger and Kritsky, 1988, A. brachycirum Boeger a nd Kritsky, 1988, A. camelum Boeger and Kritsky, 1988, and A. catalaoe nsis Boeger and Kritsky, 1988, from Pygocentrus nattereri; Amphitheciu m diclonophallum sp. n. from Pristobrycon sp., Serrasalmus compressus, S. elongatus, S. gouldingi, S. rhombeus, and Serrasalmus sp. (2 of Je gu); Amphithecium falcatum Boeger and Kritsky, 1988, from Pristobrycon sp., Pygocentrus nattereri, Serrasalmus compressus, S. elongatus, S. gouldingi, S. manuelli, S. rhombeus, S. spilopleura, Serrasalmus sp. ( 2 of Jegu), and Serrasalmus sp. (2n=58); Amphithecium junki Boeger and Kritsky, 1988, from Pygocentrus nattereri and Serrasalmus rhombeus; A mphithecium microphallum sp. n. from Pygocentrus nattereri and Serrasa lmus sp. (2n=58); Amphithecium minutum sp. n. from Pristobrycon eigenm anni, Pristobrycon sp., Serrasalmus gouldingi, and S. spilopleura; Amp hithecium muricatum sp. n. from Pristobrycon eigenmanni, Serrasalmus r hombeus, and Serrasalmus sp. (2 of Jegu); Amphithecium pretiosum sp. n . from Pristobrycon sp., Serrasalmus gouldingi, and S. manuelli; Amphi thecium prodotum sp. n. from Catoprion mento and Pristobrycon striolat us; Amphithecium speirocamarotum sp. n. from Serrasalmus elongatus; Am phithecium unguiculum sp. n. from Serrasalmus spilopleura; Amphitheciu m verecundum sp. n. from Pristobrycon eigenmanni and Serrasalmus sp. ( 2 of Jegu); Heterothecium globatum sp. n. from Serrasalmus gouldingi; Heterothecium dicrophallum sp. n. from Catoprion mento; Pithanothecium piranhus (Mizelle and Price, 1965) comb. n. from Catoprion mento, Pri stobrycon striolatus, Pygocentrus nattereri, and Pygopristis denticula ta; and Pithanothecium amazonensis (Mizelle and Price, 1965) comb. n. from Catoprion mento, Pristobrycon striolatus, and Pygopristis denticu lata. The diagnosis of Amphithecium is emended, and 2 new genera are p roposed. Heterothecium gen. n. characterized by species having a sinis trodorsal vaginal pore, a sclerotized vaginal vestibule, a male copula tory organ with 2 rami, and simple distal termination of the articulat ion process of the accessory piece. Characters distinguishing Pithanot hecium gen. n. include presence of a sclerotized vaginal vestibule ope ning on the dextrolateral surface of the trunk and a distally blunt ar ticulation process of the accessory piece extending past the tip of th e distal rod. Cleidodiscus piranhus Mizelle and Price, 1965, and C. am azonensis Mizelle and Price, 1965, are transferred to Pithanothecium.