AQUATIC NEMATODES FROM ETHIOPIA .3. THE GENUS EUMONHYSTERA ANDRASSY, 1981 (MONHYSTERIDAE, NEMATODA) WITH THE DESCRIPTION OF EUMONHYSTERA-GERAERTI N-SP

Six species of the genus Eumonhystera, one of which is new to science, are described from bottom samples of Lake Tana and two associated riv ers, River Abbay and R. Gelda, Ethiopia. E. geraerti n. sp. can be ide ntified by being the only species in the genus that combines very post eriorly positioned vulva [V% = 68.2 +/- 0.7 (67.3-69.3)] with very ant eriorly positioned amphids (Amph-ABE/LRW = 0.8). The other five specie s encountered, E. dispar (Bastian, 1865) Andrassy, 1981, E. filiformis (Bastian, 1865) Andrassy, 1981, E. pseudobulbosa (von Daday, 1896) An drassy, 1981, E. mwerazii (Meyl, 1957) Andrassy, 1981, and E. vulgaris (de Man, 1880), Andrassy, 1981, are described in detail. The identiti es of some of the already described populations of E. dispar, E. filif ormis and E. vulgaris are questioned and clearer and better ways of de fining each of these three species are suggested. A peritrophic-like m embrane on the outer side of the brush-border of the intestine of E. m werazii, a species reported here for the first time out of its type lo cality, is reported. Also, scanning electronmicrographs of sectioned a nd entire specimens of E. mwerazii are presented. All species are repo rted from Ethiopia for the first time.