OF THE HALOLIMNIC FAUNA OF LAKE TANGANYIKA. 333 



been subject to this kind of metamorphism, the great Rukwa 

 Graben strikes the Tanganyika fissure at an acute angle, and 

 it is extremely probable that this longitudinal depression, as 

 pointed out by Mr. Moore, extends across the lake and 

 reappears as the great gap in the western wall through which 

 the drainage of Tanganyika has been effected. Possibly 

 subsequent erosion may have had something to do with the 

 deepening of the primary fissure, which thus becomes a " rift- 

 valley " in the true sense of the term. After passing over 

 modern lake deposits, the Red Felspathic Grits are encountered 

 on the Lukuga as previously stated (p. 327), and extend for a 

 distance of 120 kilometres from Tanganyika, and beyond this point 

 are covered by the White Friable Sandstones which constitute 

 the upper member of Cornet's " formations postprimaires." 



It seems doubtful whether any fossils occur in connection 

 Avith the Red Felspathic Grits of Lake Tanganyika. There can 

 be no doubt whatever that the Red Felspathic Grit series of 

 Cornet is the same as the sandstone series of Mt. Waller and 

 Amelia Bay on Lake Nyassa, which is identified by Bornhardt 

 with the Karoo formation, and with which are associated the 

 so-called " Drunnnond's beds " with their Glossopteris flora and 

 fresh-water fauna fseepp. H28 and 329). At more than one spot 

 in the vicinity of the northern end of Lake ^^yassa indisputable 

 evidence of coal, fossil plants, shells and fish scales of 

 fresh-water origin have been found. It seems unfortunate that 

 the corresponding beds {i.e., the Red Felspathic Grits) of 

 Tanganvika and the Concjo basin seem to be barren in this 

 respect. At least such appears to have been Cornet's opinion, 

 and he accounts, as we have seen, for the barrenness of these 

 beds on the supposition that they were laid down in a basin on 

 the west side of the primary mountain range of what is now 

 East Central Africa.* 



* Reymond {Bull. Soc. (Jeol. France, 1885) speaks of certain " schistes 

 fossiliferes," collfcted by Giraiid in 1881, at some distance from Mpala on 

 Lake Tanganyika, which were said to contain a Cyrena and fish 

 remains {Lepidosteus). This alleged discovery on Tanganyika may be the 

 same as that mentioned by Drummond {Tropical Africa), where he 

 observed that three days north of Nyassa Giraud found in the schists 

 certain fossils which Bertrand referred to Lepidosteus and Cyrena. 

 Moreover, Moore considers that " Drummond's beds " occur at two 

 or three localities on or near Tanganyika, but as he mixes these up with 

 modern lake deposits, it is not very easy to get at his meaning, the 

 more so, since no organic remains are mentioned, other than those of 

 the lake itself. On the whole, I conclude with Cornet, that no good 

 evidence of fossils belonging to the Eed Felspathic Grit series has 

 hitherto been found in the Congo basin, of which L. Tanganyika at 

 present forms a part. 



