Pigmented, with two eyes each composed of several pigment cells and numerous retinal cells. Head rounded, with auricular slits, without auricular lobes. Pharynx not pigmented. Testes large, numerous but discrete, dorsal or ventral, and prepharyngeal. Penis large, with seminal vesicle, without diaphragm in the ejaculatory duct, and asymmetrically placed in atrium. Bursa copulatrix situated laterally or anteriorly to penis. Bursal stalk with posterior diveticulum which receives the shell glands, and the oviducts separately or combined. Bursal stalk musculature of inner longitudinal and outer circular fibres. Cocoon unknown. Inhabitants of freshwater.