2 ME. G. A. BOULENGER ON A COLLECTION 



made under more favourable circumstances, would considerably modify our views on 

 the general character of this most important section of the fauna. 



How incomplete the collection is may be partly realized from the fact that, of the 

 six species previously described from Tanganyika, only one was rediscovered by 

 Mr. Moore. His series of sketches executed from fresh specimens, free use of 

 which he has kindly given me, thus enabling me to represent some of the new 

 species in their natural colours, also indicate the existence of several fishes which are 

 unrepresented in the collection. Large fishes, owing to the impossibility of preserving 

 them, had to be left behind, and the difficulties of transport by carriers resulted in the 

 loss of several jars containing spirit-specimens. Nevertheless, small as it is, and 

 though deficient in any but typically African freshwater forms, the collection is of great 

 interest, and Mr. Moore well deserves the thanks of all zoologists for the manner in 

 which, amid so many difficulties, he has succeeded in affording us a first glimpse at a 

 fish-fauna which has so long remained a mystery. 



A study of the freshwater fishes of Africa has hitherto led to the assumption that 

 the bulk of the fauna originated in the region of the great lakes, whence they have 

 radiated towards the Mediterranean and the Atlantic and Indian Oceans — a view based 

 on the close affinity, often amounting to specific identity, of the fishes of the Nile, the 

 Niger, the Congo, and the Zambesi. The homogeneity of the fauna is absolutely 

 opposed to the conception of the great watersheds having been stocked from the sea, 

 within the geological period of which these fishes are representative, this being evident 

 even in the case of such forms as Lates and Tilapia, which are known to enter salt water. 

 Nothing contrary to this theory is brought to light by an examination of the fishes 

 obtained by Mr. Moore in Lake Tanganyika. The striking character of the Tanganyika 

 fish-fauna, as revealed by Mr. Moore's collection, is the extraordinary variety of the 

 Cichlidoe ^. This is a natural group distributed all over Africa, including Madagascar, 

 but, although rich in species, nowhere else showing within a limited area anything like 

 the modifications of structure described in this report, which have necessitated the 

 establishment of nearly as many new genera as were previously known from the whole 

 of Africa. The generalized characters of some of the Cichlidce occurring in Lake 

 Tanganyika, regarding as indicative of generalization the greater development of the 

 anal fin, consistently with the system followed in classifying their more primitive 

 allies the Centrarchidce^, and the extent of the lateral lines, both of which are 

 complete in some of the newly-discovered forms ^ afford further support to the 



^ See P. Z. S. 1898, p. 132. = Cat. Pish. 2nd ed. i. p. 2 (1895). 



^ The lateral line has usually been described as " interrupted " in the Cichlidm and otter groups in which 

 it bas a similar disposition. Tbis expression conveys a serious misconception, and I have replaced it in the 

 diagnoses oi the Cichlidce and the Serranidce allied to Plesiops by " lateral lines two," the necessity for this 

 change being particularly obvious in the case of some of the species described in this report. Fishes had no 

 doubt originally a greater number of lines of sense-organs along the body, as we may still observe in many of 



