The atopomelid subgenus Metacytostethum, genus Cytostethum, is restricted to potoroine and macropodine members of the kangaroo family (Marsupialia: Macropodidae), and the species from the former subfamily are seen as ancestral to those from the latter. A key is provided for the 13 known species, of which IO are figured and described as new: C. tasmaniense and C. intermediitm from Bettongia gaim:irdi cuniculus (Potoroinae), C. prosquamatum and C. mediosquamatum from Thylogale brimii (Macropodinae), C. postsquamatum, C. maydenense, and C. inerme from T. billardierii, C. euphallits from T. stigmatica, C. thehs from T. thetis, and C. wallabia from Wallabia bicolor (Macropodinae).