PLATE XI. 



Page. 



Figs 1 to 3, 6, and 8 to 1] . Stictopoeblla angtjlaris Ulr 18: 



1 to 3. Three specimens of the usual form of this species, natural size. 



6. Surface of an average example, x9. 



8, 10 and 11. Tangential, transverse, and vertical sections, xi8, prepared from the oldest 



example at hand. 

 9. Small portion of a tangential section X50, showing the minutely tubular character of the 



divisional line between adjoining zooecial walls. 

 Lower third of the Trenton shales at St. Paul and Minneapolis. 



Figs. 4, 5 and 7. Stictoporella angularis, var. intermedia, n. var 18; 



4. A small subfrondescent example from the base of the shales at Minneapolis. 



5. A fragment of the usual form of the variety froVn toe same horizon in Fillmore county. 



7. Surface of same xi8, showing the extreme paucity of mesopores and in the upper left 



corner a portion of one of the clusters of thin- walled zooecia. 



Figs 12 to 19. Stictoporella fronditeea Ulr 18c 



12 to 14. Three specimens of this species, natural size. The original of fig. 14 belongs to 

 the Survey Museum. It is one of a number bearing the register number 5946. 



15. Surface of original of flg. 12 xg. 



16. Tangential section of an average specimen, xi8. 



17. Small .portion of same section X50, to show the structure of the inter-zooecial lines. 



18. The basal or prostrate portion of several zooecial tubes as shown in another tangential 



section, xi8. 



19. Vertlpal section, xi8. 



Lower third of the Trenton shales at Minneapolis. 

 Figs.20and 21. Stictoporella rigida Ulr " 18C 



20. A fragment of the natural size and the greater part of it X9. 



21. Portion of same, xi8. 



Lower part of the upper third of the Trenton shales at Fountain, Minn. 



Figs. 22 and 23. Stictoporella cribeosa Ulr 184 



22. Vertical section, X18. 



23. Transverse section, X 18. (See also plate X). 



