EXPLANATION OF PLATE 5 



Figs. 1-4 Meniscophyllum minutum Simpson ; plesiotypes ; University of Cincinnati No. 



23243; x5 p. 46 



1, Transverse section, late ephebic stage ; all but two septa completely fused into ring. 



2, Transverse section, reversed, late neanic stage ; all septa extend to center. 



3, Longitudinal section ; note axial tabulae. 



4, Transverse section, reversed, early ephebic stage ; cardinal f ossula becoming apparent. 



Figs. 5-9 Vesiculophyllum sedaliense ; plesiotype ; Illinois State Geological Survey No, 3506 . p. 52 



5, Transverse section, early ephebic stage ; plesiotype ; X 5 ; secondary septa are still 

 short ; all septa rather thin, but those in the cardinal quadrants are somewhat thickened ; 

 no dissepiments. 



6, Transverse section, very early neanic stage ; plesiotype ; X 5 ; tabulae prominent and 

 septa rudimentary. 



7, Transverse section, late neanic stage ; plesiotype ; X 5 ; long thick cardinal septum, 

 thick counter septum, pinnate septal pattern in cardinal and counter quadrants, and 

 thickened septa are noteworthy. 



^/Transverse section, late ephebic stage; plesiotype; X 5; aside from following ortho- 

 genetic trend shown in fig. 5, the lonsdaleoid dissepiments are the only additional feature. 



9, Longitudinal section, ephebic stage before addition of dissepiments ; plesiotype ; X 2.5 ; 

 contorted septa are cut several places in the section so that tabulae appear to be discon- 

 tinuous. 



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