PLATE 23. 



Page. 

 Fig. 1. Placenticeeas placenta, var. intercalaris 468 



1, a. A side view of the septate type-specimen of the variety. 



l,h. A different view of same, showing the narrowly truncated and flattened, or slightly 



concave, periphery, and the sagittate form of the aperture, as indicated by a section 



of one of the volutions. 

 1, c. A septum, magnified about one and a half diameters. 



