The account begins with a brief review and discussion of recent trends in the systematics of the Megascolecidae. The genus Digaster Perrier 1872 is revised and Perissogaster Fletcher 1887 is united with it. The status of the digastric genus Didymogaster Fletcher 1886 is discussed and reasons are given for retaining the genus although Fletcher's definition no longer merits separation from Digaster. A definition of Digaster s. lat. is followed by a key to all constituent species and a discussion of morphology and affinities in the genus. Descriptions of six of the eleven species of the extended genus, based on new and/or type-material, are given, together with new information from the types of D. (= Perissogaster) nemoralis.