DISCUSSION
The specimens described here are assigned to the Atractidae (Railliet, 1917 subfam.) Travassos, 1919 because the oesophagus is clearly divided into two parts, the posterior part with a distal bulb and valve, the male is without a precloacal sucker, two spicules and a gubernaculum are present, the vulva is situated in the posterior part of the body and the female tail is pointed. The family Atractidae, at one time placed in the Oxyuroidea, was considered by Chabaud and Petter (1960) to be nearer the Cosmocercoidea and this is now generally accepted. Chabaud (1978) accepted 20 genera in the family Atractidae. Adamson and Baccam (1988) accepted 14 genera moving 5 genera to the Cosmocercidae. Khalil and Gibbons (1988) , Gibbons et al. (1995,1996) added three more genera to the family Atractidae, namely, Buckleyatractis, Podocnematractis and Diceronema respectively. The specimens described herein show some similarities to the genera Orientatractis Petter, 1966 and Proatractis Caballero, 1971. Petter (1966) erected Orientatractis for specimens described from Testudo elongata from the Botanical Gardens of the Institut Pasteur of Saigon and designated O. levanhoai as type species. Five males and three females of the type specimens, collection number 94Q, were made available to the writers by the Museum National d'Histoire Naturelle, Paris for examination. The genus is characterized by complex structures on the apical extremity, the presence of 2 lateral lips and 4 submedian lips with chitinous elements, oesophagus divided into two parts, 2 unequal spicules and a gubernaculum, females monodelphic, vulva situated near anus, uterus with numerous larvae and parasitic in reptiles. Buckley (1969) added a second species to the genus, Orientatractis leiperi from Podocnemis vogli in Colombia. Reviewing the literature on the genus and examination of the type specimens of O. levanhoai confirms that the present specimens differ considerably in appearance from the two species of Orientatractis. They differ from both the species of the genus in the absence of the four bicornate structures on the cephalic region ( the present specimens have a pair of recurved spines which appear to join near their distal margin), the absence of the two lateral lips (only four submedian lips present in the specimens described herein) and the presence of ornamentation on the dorsal surface of the body (absent in the other two species). The present specimens differ from O. levanhoai in the presence of lateral alae, the width of the body in the region of the vulva, the size of the vulva opening and the arrangement of the male caudal papillae (three pairs precloacal and five pairs postcloacal in O. levanhoai, four pairs precloacal with a single median precloacal papilla and four pairs postcloacal in the specimens described). They differ from O. leiperi in the cephalic region (flattened in O. leiperi with six lips, mouth with irregular foursided border, domed in the specimens described with protruding lips to form a funnelshaped mouth opening), the cephalic region (narrowing anteriorly in O. leiperi and slightly wider than adjacent cervical region in the specimens described), the shape of the lateral alae in cross section (rounded in O. leiperi and elongate and curved dorsally in the specimens described) and the male caudal papillae (three pairs precloacal with a single median papilla just anterior to the cloaca and six pairs postcloacal in O. leiperi, four pairs precloacal with a single median papilla just anterior to cloaca and four pairs postcloacal in the specimens described).
Caballero (1971) erected Proatractis for specimens recovered from Staurotypus triporcatus Wiegman, 1828 in the southeast of Veracruz, Mexico and assigned to the species P. parvicapiticoronata. In spite of a request for the examination of the type specimens unfortunately no specimens have so far been made available to us for study. However based on the original description of the genus the specimens described herein differ from the genus Proatractis in the presence of well developed lateral alae (absent in Proatractis), the number and arrangement of the spines on the cephalic region, the presence of the half annules on the dorsal surface of the body (absent in Proatractis), the number of pairs of male caudal papillae and their arrangement (eight in the present specimens, nine pairs in Proatractis), the shape of the gubernaculum and the difference in size of the vulvar opening and anus (small vulva which is difficult to see and a large anus in the present specimens and a large vulva and small anus in Proatractis).
The specimens described differ from all the other species of the family Atractidae in the morphological features of the cephalic region, the half annules on the dorsal surface of the body and the striated lateral alae. For these reasons a new genus has to be erected to accomodate them for which the name Paraorientatractis is proposed and a new species P. semiannulata.
Type species: Paraorientatractis semiannulata n. sp.
Type host: Podocnemis unifilis Troschel,1848
Site: large intestine
Locality: Cuminá and Trombetas rivers near Pará, Brazil
Type material: Helminth Collection of the International Institute of Parasitology, St Albans, Herts AL4 0XU, UK, holotype number B1063A, paratypes B1603B, S1094B.
