though S. galilaeus reached, and was able to establish itself in the Malebo
(Stanley) Pool upriver from Kinshasa.Figure la. Substrate-breeding tilapias (genus Tihpia): natural distribution and introduc-
tions of T. zillii, T. tholloni T. rendalli and T. guineensis. The many transfers of T. ren-
dalli in South Africa are not recorded precisely but only suggested.
DISTRIBUTION OF S. MACROCHIR AND S. ANDERSONII
These two species are sympatric in part of their range. S. macrochir lives
in the rivers and lakes of the Upper ZaTre: Bangweulu-Luapula-Mweru,
Luvua, Lufira and Upper Lualaba, which were part of the Zambezi basin
prior to their capture by the ZaTre. It also occurs in the upper Zambezi and
in the Kafue. The absence of S. andenronii from the system now belonging to
the Zaire river north of the present Zafre/Zambezi divide is evidence that its
arrival in the upper Zambezi occurred after this divide was established.
Below the Victoria Falls on the Zambezi, below the Kafue Gorges and
the Luangwa Falls, S. andersonii is replaced by S. mortimeri. But since the
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