PLATE XXI. 



Phragmodictya catilliformis. 



Page 477. 



Fig. 1. The cup of a cylindrical sj)ecimen showing the continuous longitudinal 



ridges and the septum at the base of the figure. 

 Fig. 2. The diaphragm of a similar specimen showing the fine concentric and 

 radiating lines, with a portion of the outer envelope continued 

 below. 

 Fig. 3. An expanded cup somewhat compressed, but preserving nearly the 

 entire outline. The longitudinal ridges die out toward the 

 margin of the cup. 

 Fig. 4. xln enlargement of a portion of the upper margin of the cup (ng. 3), 

 to show the crowding of the striae producing a slight thicken- 

 ing of the rim, and the gradual obsolescence of the nodes. 



The great expansion of the frond above (as represented in 

 figure 3), the finely cancellate structure of the envelope, and 

 the apparent completeness of the same along this extended 

 margin in this and several other specimens, has led to the in- 

 ference that this may be the upper extremity of the organ- 

 ism; while analogy with Euplectella would indicate the op- 

 posite end as the upper termination of the frond. 



The writer has submitted a collection of specimens of 

 this species to Prof. A. Hyatt, and a letter from him, dis- 

 cusing this question, will be given with the completed paper. 

 Fig. 5. A small cup with the septum apparently perforate. 

 Fig. 6. A very elongate cylindrical specimen preserving the diaphragm. 



Keokuk group, Indiana. 



Phragmodictya (?) crebristriata. 

 Page 000. 

 Fig. 7. Lateral view of a fragment having a curved outline and showing the 

 fine reticulation of the surface. The specimen is too imperfect 

 for satisfactory determination. Keokuk group, Indiana. 



Phragmodictya lineata. 

 Page 478. 

 Fig. 8. Lateral view of a compressed specimen showing the strong regular re- 

 ticulate striae without ornamentation of nodes or ridges, and the 

 septum at the base with an abrupt depression at the apical scar. 



Keokuk group, Indiana. 



