PLATE V. 



FIGS ' PAGE 



1. Trigonia lierzogi (Goldf.) ... ... 



Left valve of a large individual, posterior part not shown. 

 Sunday's River (2891, South African Museum collection. In 

 the figure, the umbonal region is restored from another speci- 

 men (99h). 



The ornaments of the area are well preserved, and show the 

 gradual acquirement of the transversely costate character at a 

 comparatively early stage. In T. holiibi sp. nov., the change 

 takes place more suddenly and at a later growth-stage. 



2. Trigonia rogersi sp. nov 99 



Left valve. Coega Valley, east of the railway, one mile up the line 

 from Coega station (47'2g). 



