The type-species of the cichlid fish genus Petrotilapia Trewavas 1935,
P. tridentiger, is redescribed and two new species, P. genalutea and
P. nigra, are described. These three species occur sympatrically at Monkey Bay.
Morphological differences between the three species are slight and of little diagnostic
value. Live coloration is the most important taxonomic character and can be used reliably
to identify adults of the three species. Field observations of live fishes are shown to be
of paramount importance in taxonomic studies of the genus Petrotilapia.