10 PKOCEEDINGS OF THE NATIONi^LL MUSEUM vol.84 



occipital forms tlie postero-lateral edge of the facet. Tliis is unlike Tilapia 

 in wliich tlie ineetiii!,' of prootic and basioccipital is at the postero-lateral side 

 of the apophysis, and the basioccipital not only takes no share in the facet, but 

 also none in the aitophysis. 



Comparison of this cranium with that of a young Simochromis (liagramma 

 shows a very close agreement between the two. Moreover, in the skeleton of 

 an adult 8. dlaxjramma the postero-lateral corner of each facet is formed by 

 the basioccipital. It seems therefore that Simochromis belongs to the Haplo- 

 c7iroH( (S-group and not to the Tilapia-gvoui), and the possibility of a very close 

 relationship with Pseudotropheus will have to be considered. Meanwhile this 

 species, S. hahaulii, although it so closely resembles Pseudotropheus tropheops, 

 is more like Simochromis diayramma in its pharyngeal dentition and in the 

 depth of the preorbital, and is correctly assigned to this genus. 



I defer to Dr. Trewavas' opinion in regard to the generic position 

 of S. habaulti., but I wish to point out that if Boulenger's figure of 

 the dentition of S. diagramma (Boulenger, 1915, p. 275, fig. 187) 

 can be relied on, S. habaulti differs considerably. Boulenger figures 

 the inner rows of small teeth in the upper jaw as running back 

 behind the enlarged conical lateral teeth and shows the posterior 

 projections of the lower dentition as composed of several rows. In 

 S. habauUi, on the contrary, there are three rather even rows of 

 small tricuspid treeth behind the main outer row of bicuspid ones 

 in the front of the upper jaw, but the small inner teeth are not 

 continued backward behind the lateral enlarged conical ones. Fur- 

 ther, the posterior prolongations of the lower dental patch are formed 

 on each side of the lower jaw by a single regular row of conical 

 teeth. In this, /S. hahauUi is practically identical with Pseudo- 

 tropheus and differs distinctly from Boulenger's figure of S. 

 diagramma. 



The difference between Simochromis and Pseudotropheus is cer- 

 tainly very slight, and it may be that the genera will have to be 

 merged, unless hitherto unknown cliaracters are employed. This 

 brings up the question of the autochthonous nature of certain of the 

 Tanganyika and Nyasa genera. If Simochromis and Pseudotropheus 

 are indeed convergent rather than identical stocks, the parallelism 

 is astounding. 



Four very small specimens, U.S.N.M. no. 84118, 15 to 31.5 mm in 

 standard length, from Ujiji, are placed here with great hesitancy. 

 They have the posterior extensions of the dentition uniserial, but in 

 conical lateral teeth of the upper jaw are little developed. They 

 have the rounded snout of S. bahauiti and the same general form, 

 but the body is slenderer (about 3.5 in the largest example) and the 

 head is shorter (3.3 in the largest). The counts of the t^Yo largest 

 ones are: Dorsal XVII-9 and XVI-8, anal 111-7 in both, lateral 

 lines 23 + 9 and 22+10, and lateral scales 30 and 32. These examples 



