342 W. H. HDDLESTON, ESQ., M.A., F.R.S., ON THE ORIGIN 



Tanganyika has been examined in detail, and it has been shown 

 that this lake, like all other great lakes of Central Africa, 

 contains the ordinary fresh-water fauna of the continent ; but 

 that in Tanganyika, and in Tanganyika alone, there are a number 

 of organisms possessing definitely marine and somewhat archaic 

 characters. Along with these, the halolimnic members of the 

 Tanganyika fauna, there are others, such as the prawns, sponges 

 and protozoa wdiich, although not like the previous types, 

 unique in being found in Tanganyika for the first time as fresh- 

 water forms, are notwithstanding probably portions of the same 

 group, for they are peculiar to Tanganyika, and are not 

 characteristic of the general fresh-water fauna of the African 

 continent." He further suggests that the African ganoids and 

 certain otlier members of the African fish fauna may be portions 

 of the " haloliuniic " fauna. Lastly, he points to the significance 

 of the similarity which subsists between the shells of the 

 halolimnic gasteropods and " the remains of those found in the 

 deposits of the old Jurassic seas." 



Thus far Mr. Moore. When we ourselves attempt to face the 

 Tanganyika Problem, it is obvious that it will have to be 

 considered both from a zoological and a geological point of view, 

 and the question is which shall we consider first, the zoology or 

 the geology ? We are dealing with an exceptional fauna, 

 occurring under peculiar conditions and in what was, until quite 

 recently, a most out-ol'-the-way place. Perhaps the first 

 question we should ask ourselves is this : Do we consider that 

 there is sufficient evidence of the marine origin of the halolimnic 

 fauna ? This fauna is placed l)y j\Ir. ]\Ioore himself under two 

 different categories. (1) The halolimnic gasteropods, which are 

 thought to be homceomorphic with certain shells from beds of 

 the Inferior Oolite formation in Western Europe, and are thus 

 inferentially regarded as descendants of those forms. (2) A 

 fauna, not so thoroughly exceptional as the halolimnic 

 gasteropods, made up of prawms, sponges, protozoa, etc., which 

 are archaic in type and njay be portions of the same group of 

 marine derivatives. Tlie presence of Mcchisa also is held greatly 

 to strengthen this view. As regards the portion of the argument 

 relating to the fishes it has been stated by a competent authority 

 that the fishes described by Mr. Eoulenger in Mr. Moore's 

 beautiful book are all essentially present day types, and do 

 not in any way represent survivors from the seas of the 

 Mesozoic period.* 



Geological Magazine, September, 1903, p. 418. 



