TISHES FKOM LAKE TANGANYIKA — MYERS 9 



SmOCHROMIS BABAULTI Pellegrrin 



Simochromts hahaulti Pellegkin, 1927, p. 50O (Ouvira, Lake Tanganyika) ; 1928, 

 p. 82, fig. 1 (figure of type). 



Four specimens, U.S.N.M. no. 84129, the largest 61 mm in standard 

 length, are from Kigoma; one has been partially skeletonized, and 

 another has been presented to the British Museum. 



This species has hitherto been known from a single specimen of 

 approximately the same size as our largest one. The four examples 

 show the following counts : Dorsal XVI-9 ; XVI-9 ; XVII-9 ; XVI-9. 

 Anal III-8 ; III-8 ; III-7 ; 111-7. Pectoral 16 in all four. Lateral 

 lines 21 + 10, 21 + 12, 22 + 11, 21 + 12. Lateral scales 29, 30, 29, 30. 

 Gill rakers on upper and lower limbs of first arch 3 + 7 in all four. 

 Bicuspid teeth in first row in upper jaw 25, 29, 28, 24. Caudal 

 truncated. Head about 3 in standard length. 



There are 8 or 9 rather wide, vertical, dark bands on a lighter 

 background. Head rather dark, lightening on opercles, on throat, 

 and on breast. Base of pectoral rather dark. Fins nearly plain 

 except for a dark longitudinal streak through tlie membranes of 

 the first six dorsal spines in one example and a faint darkening of 

 the lappets at the fin edge. 



An interesting problem has arisen concerning the systematic posi- 

 tion of this fish. In his review of the Tanganyika genera, Regan 

 (1920a, p. 35) places Simochromis in the Tilapia group, which 

 is characterized by the exclusion of the basioccipital from the articu- 

 lar surface of the upper pharyngeal apophysis. In examining the 

 dentition of S. habaulti I was struck with its remarkable similarity 

 to that of the Nyasa Pseudotropheus tropheops (Regan, 1921, p. 681, 

 fig. 2a). This had, indeed, already been noted by Pellegrin. Fur- 

 ther, S. habaulti has much of the appearance of P. tropheops^ but 

 Pseudotropheus is a member of the Haplochroinis group, in which 

 the basioccipital enters the facet of the upper pharyngeal apophysis. 

 Examination of a cranium of S. hahaulti was not wholly satisfactory, 

 owing to the small size of the specimen and my unfamiliarity with 

 the group. 



Dr. Ethelwynn Trewavas, of the British Museum, has been so kind 

 as to examine this cranium of S. hahaulti (as well as a complete 

 specimen) in the light of her extensive knowledge of the Afriaan 

 Cichlidae. She writes: 



I agree with you tbat the pharyngeal apophysis is not of the Tilapia type ; 

 neither is it of the typical Haplocliromis type. It is a young fish with the 

 pharyngeal apophysis very weakly developed, but it is possible to see that 

 the basioccipital does not contribute to the facets for the pharyngeal. Never- 

 theless it (the basioccipital) extends forward so as to meet the prootic at the 

 antero-lateral side of the facet, and the suture between parasphenoid and basi- 



