Plate LIX Continued. 



PAOB. 

 Fig. 6. POLYPOKA EETBOKSA Ulr ............................................................ 591 



6. Obverse surface, x9. 



6 a. Portion of same, x!8, showing the obliquely elevated peristomes. 



6 b. Reverse face of another example, x9. showing the oval fene.strules and 



nodulose branches. 

 6 c and 6 d. Thin sections showing the structure of the zoarium at differ- 



ent levels, x!8. 



Eeokuk group, Keokuk, Iowa. 



E. O. Ulrich's collection. 



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