A new description is given of Pseudotropheus williamsi (Günther). Recognition of the dental resemblances between Pseudotropheus williamsi and Melanochromis melanopterus, type-species of their respective genera, shows that a generic distinction based on the dentition cannot be maintained.
The genera are redefined, and a new subgenus is proposed for Pseudotropheus tropheops and related species.
Pseudotropheus livingstonii (Boulenger) is described on the reasoned assumption that
specimens from the Southeast arm of the lake Malawi [sic] are conspecific with the holotype,
a juvenile. Species showing the same pigment pattern are compared.