EXPLANATION OF PLATE XXXIII. 



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FIG. 1. Archimedes wortheni 26 



A large example. (Cox collection.) 

 Carboniferous, Keokuk limestone. 



FIG. 2 . Archimedes owenanus 26 



A typical specimen. (Mns. Mo. Geol. Sur.) 

 Carboniferous, Keokuk limestone. 



FIG. 3 . Phacelopora pertenuis 13 



Part of a zoarium. (After Ulrich.) 

 Silurian, Trenton limestone. 



FIG. 4. Rhombopora lepidodendroides 35 



4a. A large example. (Hare collection.) 

 4b. Surface. (Enlarged ) 



Carboniferous, Upper Coal Measures. 



FIG. 5. Glyptopora plumosa 20 



Fragment. (After Ulrica.) 

 Carboniferous, St. Louis limestone. 



FIG. 6. Thamniscus furcillatus 31 



Fragment. (Enlarged, after Ulrich.) 

 Carboniferous, Kaskaskia limestone. 



