PLATE 6 



Fig. i. Hy st richosphaeridium tubife rum (Ehrenberg). Holotype. Slide XXV. Flint 

 from Delitzsch. Humboldt-Universitat, Berlin. Apical view. X400. 



Fig. 2. Hyst richosphaeridium tubiferum (Ehrenberg). Holotype. Medial view. X400. 



Fig. 3. Hystrichosphaeridium readei sp. nov. Holotype, PF. 3030(2). X500. 



Fig. 4. Hystrichosphaeridium deanei sp. nov. Cenomanian (borehole depth, 690 feet). 

 FM. 690/12(2). X400. 



Fig. 5. Cleistosphaeridium ancoriferum. Cenomanian (borehole depth, 810 feet). 

 PF.3044(i). X500. 



Fig. 6. Hystrichosphaeridium mantelli sp. nov. Holotype, PF.3032(i). X500. 



Fig. 7. Tanyosphaeridium variecalamum gen. et sp. nov. Holotype, PF.3035(2). 

 X500. 



Fig. 8. Hystrichosphaeridium deanei sp. nov. Holotype, PF.303o(i). X500. 



