PLATE XV. 



PAGE. 



FigS. 1 tO 6. MONTICTJLIPORA (?PRASOPORA) QKANDIS Ulr 219 



1. A small lot Kite mass of the natural size. 



2. Fragment of a subramose example, natural size. 



3. Surface of same xg. 



4. Several zooecia of same, xis, exposing the cystiphragms. 



5. Tangential section xi8. 



6. Three portions of a vertical section, xis, showing extremes of variation in the tabula- 



tion of the zoo3cial tubes. Mus. Keg. No. 5969. 

 Base of the Trenton shales at Minneapolis. 



Figs. 7 and 8. MONTICULIPORA WETHERBYI ?Ulrich 218 



Tangential and transverse sections, xis, of a specimen from the Trenton limestone at 



Minneapolis. Mus. Reg. No. 5967. 



FigS. 9 tO 12. MONTICULIPORA INCOMPTA, n. Sp 219 



9. Tangential section xis. 



10. Small portion of same xso, showing the peculiar structure of the walls. 



11. Vertical section xis. 



12. One of the walls xso. 



Middle third of the Trenton shales, Minneapolis. Mus. Reg. No. 5968. 



Figs. 13 to 15. ATACTOPORELLA INSUETA, n. sp 224 



13. A crinoid column covered with the zoarium of this species, natural size. 



14. Tangential section xis. 



15. Portion of same xso. (See also plate XVIII.') 



Middle third of the Trenton shales at Minneapolis. Mus. Reg. No. 5985. 

 Figs. 16 and 17. ATACTOPORELLA TYPICALIS, var. PR^ECIPTA, n. var 223 



1 6. Vertical section x 18. 



17. Tangential section xso. (See also plate XVIII.) 



Middle third of the Trenton shales, Minneapolis. Mus. Reg. No. 5984. 



Figs. 18 to 21. ATACTOPORELLA CRASSA, n. sp 225 



18. Tangential section x is. 



19. Small portion of same, xso, showing the structure immediately beneath the surface of a 



matured example. 



20. Another portion of same X50, showing the appearance at a deeper level in the zoarium. 



21. Vertical section, xis. 



Galena shales near Cannon Falls, Minn. 



