688 SYDNEY H. BALL AND MILLARD K. SEALER 



the rock as flat-lying, "gres tendre," the common Belgian name 

 for the Lubilache formation. The matrix in which the fossil 

 occurs is typical of the soft sandstone seen by the authors at 

 Lusambo, 60 miles to the north of Sangula. There is then no 

 doubt in the minds of the writers that this is from the Lubilache 

 formation. Concerning this fossil Dr. Ulrich says: 



It is a bivalved crustacean, apparently of the genus Estheria: and so far 

 as known to me the largest species of this genus yet found. The species seems 

 distinct from all the described forms. 



Looking over the fossils again, my belief has grown to conviction that the 

 bed from which these fossils were procured is Mesozoic and Jura-Triassic, 

 rather than later. ' 



While the fossils are by no means strongly indicative of the 

 climatic conditions under which they lived, Dr. Ulrich states that 

 if they indicate anything concerning the climate it would be that 

 it was relatively moist and rather cool. The water was either 

 fresh or brackish. 



DEPOSITION OF THE LUBILACHE 



The Lubilache formation was deposited. in a Triassic lake of 

 fresh or brackish water, which may have been connected with the 

 ocean. On the railroad at kilometer 115, in the Lower Congo, 

 residual bowlders of what one of us (S. H. B.) takes to be the 

 Lubilache formation, occur on the west side of the present divide 

 of the plateau, commonly called the Crystal Mountains. It is 

 hence more than probable that this ancient lake was once connected 

 with the ocean by one or more straits. From the present dis- 

 tribution of the Lubilache beds this lake was at least 900 miles 

 in diameter, and was probably much larger. The bed of the lake 

 was an undulating surface, and the body of water was surrounded 

 by low land to the west, north, and south, but with at least hilly 

 country to the east. These eastern hills in instances must have 

 been 2,000 feet high. Between them ran valleys, some of which 

 appear to have been deep and abrupt enough to have been worthy 

 of the name of "fjords." While the Lubilache was being deposited 

 it is more than likely that the central part of the lake basin around 

 the present Lake Leopold II was a sinking area. At no time does 

 the lake appear to have been deep, except in certain valleys extend- 



