A4 Dr. E. Lénuberg on 
the same opinion. There is, however, another possibility, 
namely, to regard Gephyrochromis as a subgenus of Tilapia 
and unite under the former name such species of Tilapia 
which, when fully adult, acquire an outer enlarged series of 
simple, unicuspid, conical teeth. Iam uncertain, however, 
if this would be suitable, because the development of such 
teeth instead of the bicuspid TZi/upia-teeth is no doubt 
an adaptation to a certain kind of diet* that could have 
taken place quite independently several times, and in species 
of Tilapia of a rather remote kinship. If this is the case, 
a subgenus Gephyrochromis would include a number of 
fishes similar in consequence of a parallel adaptive develop- 
ment, but without close genetic affinity, and that would, of 
course, be unsatisfactory. For want of material I cannot 
express any certain opinion, but must leave the question open 
for the present. 
The genus Gephyrochromis, hitherto monotypic, was origi- 
nally established on a fish discovered by Mr. J. HE. S. Moore, 
and named after him G. Moor. The fish from the Hlephant 
Lake, Cameroon, fully agrees with regard to the dentition on 
which the generic diagnosis was founded, but differs in other 
respects a good deal from the first-mentioned type. The 
Cameroon fish has a larger head, longer snout, smaller eye, 
smaller number of dorsal spines, but larger number of soft 
rays, as well in dorsal as anal fins, and smaller number of 
scales in a longitudinal series. ‘The general outline of the two 
species is also different. Among the true Tilapie the fish 
from the Elephant Lake most nearly approaches Tilapia 
macrocephala. In addition to the distinguishing characteristic 
deduced from the dentition the following differences may be 
enumerated :—-Tvlapia (Gephyrochromis) Linnellit has a 
larger head, the length of which is much longer than the 
depth of the body, while in 7. macrocephala the opposite 
is the case. The snout of 7. Linnellit is longer when com- 
pared with the diameter of the eye, which latter, even in my 
youngest specimen, is contained fully twice in the former, but 
in ZT. macrocephala not more than 13 times. The eye of the 
former is smaller, even in the youngest contained 5 times in 
the length of the head, but only “4 to 43” in 7. macro- 
cephala. The interorbital breadth of 7. Linnell is also 
somewhat larger. Its last dorsal spine is the longest, but 
comparatively much shorter thanin 7. macrocephala. In the 
latter it is said to be 40 °/, (=#) of the length of the head, 
but in the former it varies between 27:5 and 30 °/, of the 
* Probably more carnivorous than that of other species of Tvlapia, 
