PLATE XL 



PAGE. 



Figs 1 to 3, 6, and 8 to 11. STICTOPORELLA ANGULAUIS Ulr 182 



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



6. Surface of an average example, X 9. 



8, 10 and 11. Tangential, transverse, and vertical sections, x 18, prepared from the oldest 



example, at hand. 

 9. Small portion of a tangential section xso, 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. INTEBMEDI A. n. var 1 83 



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



5. A fragment of the usual form of the variety from tne same horizon in Fillmore county. 



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



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



Figs 12 to 19. STICTOPORELLA FRONBIFERA Ulr 183 



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 fig. 12 xg. 



16. Tangential section of an average specimen, xig. 



17. Small portion of same section xso, to show the structure of the inter-zoo?cial lines. 



18. The basal or prostrate portion of several zocecial tubes as shown in anqther tangential 



section, xis. 



19. Vertical section, xis. 



Lower third of the Trenton shales at Minneapolis. 

 Figs. 20 and 21. STICTOPORELLA RIGID A Ulr 180 



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



21. Portion of same, xis. 



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



Figs. 22 and 23. STICTOPORELLA CRIBROSA Ulr 184 



22. Vertical section, xis. 



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





