PLATE XV. 
Figs. 1 to 6. MONTICULIPORA (?PRASOPORA) GRANDIS UIP... .....-2- 02s eeeeee eee e eee ene cee se ee ceee 219 
1. A small lobate mass of the natural size. 
Fragment of a subramose example, natural size. 
Surface of same *9. 
Several zocecia of same, X18, exposing the cystiphragms. 
Tangential section <18. 
Three portions of a vertical section, X18, showing extremes of variation in the tabula- 
tion of the zocecial tubes. Mus. Reg. No. 5969. 
Base of the Trenton shales at Minneapolis. 
Figs. 7and 8. MONTICULIPORA WETHERBYI PUITICH...........0 2c eee ete eee eee tone ete tens ence 218 
Tangential and transverse sections, X18, of a specimen from the Trenton limestone at 
Minneapolis. Mus. Reg. No. 5967. 
Figs. 9 to 12, MONTICULIPORA INCOMPTA, Te SP occ ce cce. eee wnc ences = velne semen ocean snccsers=oree 219 
9. Tangential section X18. 
10. Small portion of same 50, showing the peculiar structure of the walls. 
11. Vertical section <18. 
12. One of the walls X50. 
Middle third of the Trenton shales, Minneapolis. Mus. Reg. No. 5968. 
Figs: 13) todd. “ATACTOPORELUATINSUEDA =D. SPs sc aeicl/c ele elotale fe o1c'n cl= stole Cleis efetals tw avelvle]oielsis[aielaitelelele sie/=!uisie 224 
13. A crinoid column covered with the zoarium of this species, natural size. 
14. Tangential section X18. 
15. Portion of same x50. (See also plate XVIII.) 
Middle third of the Trenton shales at Minneapolis. Mus. Reg. No. 5985. 
Figs. 16 and 17. ATACTOPORELLA TYPICALIS, Var. PRACIPTA, D. VAP... 2. seus ccseneme recess ernssene 223 
16. Vertical section <18. 
17. Tangential section *50. (See also plate XVIII.) 
Middle third of the Trenton shales, Minneapolis. Mus. Reg. No. 5984. 
Figs. 18 to 21. ATACTOPORELLA CRASSA, DT. SP... esc eece en cece cece ences ee tecees cae cere cece ccece 225 
18. Tangential section <18. 
19. Small portion of same, x50, showing the structure immediately beneath the surface of a 
matured example. 
20. Another portion of same 50, showing the appearance at a deeper level in the zoarium. 
21. Vertical section, 18. 
Galera shales near Cannon Falls, Minn. 
Ga RAUS BS ES 
