OP THB HALOLIMNIC FAUNA OF LAKE TANGANYIKA. 365 



This completes the periphery of the Congo basin as at present 

 constituted. 



Suggested correlation of the beds composing the interior of the 

 hasin. — Having completed the circuit of the Congo basin, we 

 must next endeavour to ascertain something of the geological 

 history of this vast tract and its constituent elements. The 

 first question we ask ourselves must be, what is the approxi- 

 mate age of these two great interior sandstone formations ? 

 Without fossils, terrestrial, fresh-water or marine, to guide us, 

 this can only be done by way of inference and analogy.* 

 Cornet calls them post-primary, i.e., to say, they rest in almost 

 horizontal layers, for the most part, either on crystalline rocks 

 or on old palaeozoic rocks inclined at high angles. This is very 

 much the case with the Karoo beds at the Cape, which are in 

 position analogous to the two sandstone series of the Congo. 

 The Karoo beds fortunately contain a fairly abundant fauna 

 and flora, which is wholly terrestrial and fresh-water. The 

 geological position of the Karoo beds is pretty well known, and 

 I must refer to a previous statement on this subject (see page 

 oo3). We are not altogether without links in the chain of 

 evidence. 



A paper appeared lately in the Quarterly Journal of the 

 Geological Society by Mr. Molyneuxf on "The Sedimeotary 

 Deposits of Southern Khodesia," where a provisional classifica- 

 tion of the several formations, down to the Zambesi, was 

 suggested. Beneath a series of sandstones and grits, capped by 

 volcanic rocks, occur some 800 feet of beds containing 

 workable and impure coal and also some recognizable fossils 

 (Matobola beds). The interest of these consists in the fact that 

 scales of the fisli Acrolepis were recognized, the genus also 

 occurring in the Lower Karoo, and likewise in the so-called 

 " Drummond's beds " on Lake Nyassa. A very few lamelli- 

 branchs were obtained from the Sengwe coal-field and were 

 described by Dr. Hind. These are small, oval, gibbose bivalves 

 belonging to the genus Falaeom-utela, similar to species from the 

 Permian of the Volga. A few plant remains were collected, 

 and amongst others fronds of the fern-like plant Glossopteo-is 

 Broivniana, Brongn, and of some of its varieties. There can be 

 very little doubt, therefore, that the Matobola- beds of Southern 

 Ehodesia may be referred to the terrestrial and fresh-water 

 Lower Gondwana system of Permo-Carboniferous age. The 



* This was Prof. Cornet's view at the time he wrote, 

 t Vol. 59 (May, 1903) p. 266. 



