PLATE IV. 



1. Trigonia rogersi sp. nov 99 



Dorsal view. Bare slope W. 30 S. from the middle of Barkly 

 Bridge, on the farm Olif ant's Kop (20h). 



2. Trigonia Jiolubi sp. nov 103 



2. Left valve ; 2a, frontal aspect of same specimen, showing both 

 valves. Left side of Coega Valley, half a mile down from the 

 railway (458g). In fig. 2, a portion of the shell is missing from 

 the lower part of the valve ; in the drawing, the ribs have been 

 restored in this part and the ornaments supplied by copying the 

 corresponding part of the right valve. 



