Fauna and Stratigraphy of the Stormberg Series. 465 



Southern Rhodesia"; while Molyneux says "I agree that the Lubilash 

 series much resemble (in petrological features) the escarpment grit 

 and forest sandstones. Thus it must be that the Lubilash are my 

 escarpment-forest series, and of Upper Karroo age. The chalcedonic 

 segregations, agates, and other silifications, and the friable nature of 

 his line sandstones are remarkably akin to features of the forest 

 sandstones of Mafungabusi Mountains, where there is no doubt that 

 they overlie the coal measures." As has been shown, the Forest 

 Sandstone is almost certainly the equivalent of the Cave Sandstone. 

 More pal aeon tological evidence is, however, greatly desirable, as simil- 

 arity of petrological features merely means similarity of conditions 

 of deposition and need not of necessity imply similarity of age. The 

 Estheria sp. described by Leriche seems to have a fairly close resem- 

 blance to the Cave Sandstone form from the beds at Siberia C.I'.; 

 and their occurrence in a thin shaley band in massive sandstones is 

 certainly significant when compared with the mode of occurrence of 

 the latter. 



Most writers on the geology of the Belgian Congo follow Cornet's 

 original idea of the lacustrine origin of the Lualaba and Lubilache 

 series. For example, Ball and Shaler picture their "Lubilache series" 

 as having been formed in a lake which was probably subsiding in 

 the middle, with low land to the west, north and south but hilly 

 ground to the east - - the hills possibly rising to a height of 2000 feet. 

 Between these latter ran valleys, some deep enough and narrow enough 

 to be worthy of the name of "fiords". No where was the lake deep. 

 Cross-bedding was common, as well as abrupt changes from sandstone 

 to shale. There was deep disintegration of the rocks of the shore-line 

 due to weathering. Cornet, however, writing in 1910 remarked with 

 regard to the "Lac Lubilachien" that his views had undergone modi- 

 fication since 1893. The conception of Lake Lubilache was a simple 

 one and provisionally admissible at that time. But the Lubilache 

 series, which is far from being limited to the stretch of the actual 

 basin of the Congo, is much more complex than was at first supposed. 

 It is possibly in part of lacustrine origin; but dunes and aeolian 

 sediments generally play an important role in it. The "gres poly- 

 morphes", which are so characteristic of the system are certainly 

 desert formations. Passarge follows Cornet in considering the Lubi- 

 lache Beds as the products of a desert climate. 



