Freshwater bottom samples collected from Ethiopia during December 1993 and January 1994 yielded six species of the genus Monhystera Bastian, 1865 of which four are new to science.
Each of the four new species can be recognized by a combination of characters; Monhystera shibrui n. sp. can be identified by the presence of a dorsal denticle, post-vulval gland cells, short vagina, and its viviparity, M. tanae n. sp. by the offset lip region, short cephalic setae, short vagina, possession of a pair of posterio-dorsolateral vaginal gland cells, more posteriorly situated vulva, lack of post-vulval gland cell, shorter vulva-anus distance compared to tail, its viviparity, short spicules, and short gubernaculum, M. nubiae n. sp. by its long vagina, presence of a pair of post-vulval gland cells and a very sharp, arrow-head shaped spinneret tip, and M. deleyi n. sp. can be recognized by the attenuated anterior end with narrow lip region, relatively wide amphids compared to corresponding body width, long vagina, presence of post-vulval gland cell, and cardia with three gland cells. Detailed descriptions of M. cf. gabaza Joubert & Heyns, 1980 and M. somereni Allgén, 1952 are also given. While both species are reported here for the first time from Ethiopia, the former is reported for the first time out of South Africa and the need for more information on its type population is stressed. Lateral line is reported here from two species, M. deleyi n. sp. and M. cf. gabaza Joubert & Heyns, 1980, for the first time in the genus. Scanning electromicrographs of four species, M. Shibrui n. sp., M. nubiae n. sp., M. deleyi n. sp. and M. cf. gabaza, are also given.
Structures used in species identification in the genus Monhystera are reviewed. It is recommended, in future species descriptions in the genus, to use labial setae in addition to the use of cephalic setae, actual vaginal length in addition to its ratio to the corresponding body width both in females without and females with eggs but separately, a full and detailed description of the cells of the reproductive system and coelomocyte distribution, and to include an enlarged illustration of the spinneret outlet.