PLATE XX. 



ECTENODICTYA ECCENTRIC A. 

 Page 476. 

 Fig, 1. A specimen obliquely compressed showing the concentric and radiat- 

 ing lines from the eccentric apex. 



Keolcuh group, Indiana. 



Phragmodictya catilliformis. 

 Page 477. 

 Figs. 2, 3. Lateral and vertical views of a small specimen, showing the dia- 

 phragm. Keokuk group, Indiana. 



Physospongia Dawsoni, Whit/ield, sp. 

 Page 479. 



Fig. 4. Lateral view of an infundibuliform specimen showing some of the 

 nodes extended into spiniform processes. 



Fig. 5. A fragment showing the arrangement of the nodes and depressions- 

 Some of the nodes are broken off, and a few of the depressions 

 are filled with the surrounding rock. 



Fig. G. A small example of the same species. 



Fig. 8. Two nodes and corresponding depressions enlarged to show their al- 

 ternate arrangement, and the acicular spicules forming the sub- 

 stance of the envelope. Keokuk group, Indiana. 



Physospongia Colletti. 

 Page 480. 

 Fig. 7. A portion taken from near the aperture of a large individual, showing 

 the irregular arrangement and large size of the nodes. 



Keokuk group, Indiana. 



Physospongia alternata. 

 Page 481. 

 Fig. 9. A cylindrical fragment showing the broad alternating nodes and de- 

 pressions, with narrow, concentric and longitudinal cinctures. 



Keokuk group, Indiana. 



ECTENODICTYA EXPANSA. 

 Page 475. 

 Fig. 10. A large fragment showing an obscure concentric and radiating ar 

 rangement of the surface lines, and several nodes and ridges 

 upon a portion of the periphery. 



Waverly group, Warren, Pa. 



