Hi Classification of the Family Cichlide. 
The above data enable the origin and relationships of the 
Cichlid fauna of Lake Tanganyika to be discussed. 
Tylochromis is found in the Congo and in West Africa, 
and is represented in ‘Tanganyika by a single species; it 
is an isolated genus, whose nearest relative is Ptychochromis 
of Madagascar. Of the large African genus Tilapia only 
the widely-distributed 7. nilotica has reached Tanganyika, 
apparently through L. Kivu; the endemic eotilapia has 
the structure of J. nilotica and its allies, but differs in its 
dentition, having all the teeth tricuspid. 
A small group of endemic genera begins with Limnotilapia, 
which is nearly related to, but is in some respects more 
generalized than Tilapia, and leads on the one hand to Lobo- 
chilotes and on the other to Gephyrochromis, Simochromis, and 
- Tropheus ; in this group the Limnotilapia dentition (outer 
teeth bicuspid, inner tricuspid) undergoes various modifica- 
tions; Lobochilotes, teeth compressed, unicuspid; Gephyro- 
chromis, outer teeth conical ; Simochromis and Tropheus, 
anterior outer teeth bicuspid, lateral conical. 
Another little group of endemic genera commences with 
Opkthalmotilapia, which is closely related to Limnotilapia, 
but has all the teeth tricuspid (or sometimes unicuspid), 
small, and fixed. ‘This genus has given rise to Cyathopharyna, 
distinguished by the small scales and the form of the lower 
pharyngeal, and to Cunninglonia, Asprotilapia, and Petro- 
chromis, in which the tricuspid teeth are long, slender, and 
movable. It is interesting to note that the total number of 
dorsal rays is nearly the same in Petrochromis as in the 
other genera, but that the spines have increased at the 
expense of the soft rays; this genus has a species in 
L. Nyassa, but there can be little doubt that it originated in 
Tanganyika. 
The endemic Limnochromis, with conical teeth, does not 
differ very essentially from Limnotilapia in other characters. 
Cyphotilapia lias one species from Tanganyika and another 
from the Upper Congo; if, as seems likely, this genus is 
Limnochromis specialized, it probably originated in the lake. 
The monotypic Boulengerochromis .is essentially a small- 
scaled Limnotilapia, aud Perissodus seems to differ from it 
only in the peculiar dentition. 
‘he seventeen genera mentioned above have the pharyngeal 
apophysis formed by the parasphenoid alone; two( Zylochromis, 
Tilapia) are widely distributed genera, each represented in 
the lake by a single species; one endemic genus (Nevti/apia) 
is closely related to Tilapia ; the rest may have originated in 
the lake from a single ancestral type, which Limnotilapia 
