200 DiCTVOSPONGID/E. 



PLATE I. 



CYATHODICTYA, nora. propos. 



Page 24. 



Cyathodiotya reticulata, Walcott (sp.). 



Page 21. 



Figures 1-6. A series of young specimens, all of natural size, showing grada- 

 tion in form, and most of them retaining the reticulum more or less 

 completely. 



Figure 7. An unusually large example, its spicular structure somewhat con- 

 ventionally reconstructed in places, showing the arrangement of the 

 spicular elements and, beneath the reticulum, the irregularly dis- 

 tributed areoles outlined in an unresolvable mass of pyrite. 



Figure 8. The apertural portion of an average cup, torn at one side ; enlarged 

 to show the finer spicular net- work about the margin, x 3. 



Figure 9. An individual of somewhat less than average size. 



Figures 10,11. The apertural extremities of two individuals. The apparent 

 thickness of the spicular wall is due to slight incurvature about the 

 apei'ture. x 3. 



Figure 1 2. The basal extremity of an average specimen ; showing the exten- 

 sion of the reticulum into a short basal tuft, x 3. 



Figure 13. An enlargement of a portion of the reticulum, showing the differ- 

 ent series of simple cruciform spicules, and the underlying layer with 

 its areoles. This inner layer is unresolvable, its substance as 

 preserved being granular pyrite. It will be observed that the 

 areoles are irregularly disposed and are covered by spicules of the 

 outer frame- work, x 5. 

 Utica slate. Holland Patent, New York. 



SPH^RODICTYA, gen. nov. 



Page 26. 



Sph^eodiotya suBSPHiERicA, Walcott (sp.). 



Page 26. 



Figure 14. A cluster of young individuals of various sizes, showing 

 peripheral spicules on some of the specimens. 



