The adult body is elongate or occasionally oval or subglobular, sometimes with fine spines. The suckers are well-developed and usually at the anterior end. There is usually a prepharynx, the pharynx is muscular, the oesophagus, if present, is short and the caeca long, terminating near the posterior end. The gonads are posterior to the ventral sucker and the genital pore opens on the ventral surface.