Fishes from the Cameroon. 45 
same measurement. The pectoral of JZ. macrocephala is 
decidedly longer than the head, but in 7. Linnellet a good 
deal shorter than the head. On the other hand, the ventrals 
are shorter in the latter, not reaching the anus. 
Tilapia (Gephyrochromis) Linnellit seems accordingly to 
be quite a distinct species. To allow further comparison I 
append a table of comparative measurements of two specimens 
(not the same as used for the diagnosis) :— 
Total length without caudal fin ............ 163 mm. 147 mm. 
Length of head in °/, of total leneth ........ 44-7 42:8 
DEEHEGMO OCG ls siete scrsid ie fe arauilel cease asi 6s 38'0 38'°7 
Distance from snout to anal fin.............. 74:8 74:8 
o Fe rs VENETIAN era Wee ee 45°3 46:9 
Mewoihsor pectoral. 2... Sccca deeds vetoes 06°1 36:0 
; VOUT ken Can Ree OR Ne 22°7 24-4: 
Mepriboimeaudal peduncle: ...5..5.2552 6s. 08 13'8 14:2 
Length of ,, chm) eRe RRL O een 13:1 12:9 
Diameter of eye in °/, of length of head...... 20°5 19:0 
MeO GIIBONESTIOUG) ans-c0-tcrs w'cletc) 1a a -sidisie(p sare vs 42-4 39°6 
Mimeroniialybreadth: wc. caine gs cee cue val cles 35°6 39'6 
enotheor last dorsal spine “oss 05.5 cba ce 27-5 30'1 
The specimens of Z%lapia (Gephyrochromis) Linnellit were 
collected in the Elephant Lake, which is situated N.N.E. from 
the Cameroon Mountain, 9° 22’ KE. long., 4° 39’ N. lat., and, 
according to Andrée’s map of 1901, 320 m. above the sea. 
The Swedish civil engineer P. Dusén, who has visited this 
lake, puts its altitude above the sea-level at 285 m., and 
informs us that itisa typical crater-lake*. Itis now drained 
by a tributary to the Mungo River; the former finds its way 
from the lake through the narrow Barombi cleft. In former 
times, however, Mr. Dusén thinks that the lake was drained 
through a now dry river-bed to the Meme River. The dis- 
tance between the Elephant Lake and the sea along the Mungo 
River and its tributary is probably about 90 or 100 kilo- 
metres. In such a case this crater-lake seems to be rather 
isolated, and its fauna must be of great interest from a 
zoogeographical point of view. 
Tn addition to the fishes described above, Mr. G. Linnell has 
sent me some Crustacea from the Hlephant Lake, namely, 
Potamonautes africanus (A. Milne-Edw.) and Palemon 
(Bithynis) jamaicensis Vollenhovent (Uerklots). Both species 
were represented by very large and beautiful specimens, and 
seem consequently to flourish very well in the Hlephant Lake. 
#* Geol, Foren. Forh, no, 155, Bd. xyi. (Stockholm, 1894), 
