PLATE XVI 



PAGE. 

 Figs. 1 to 10. PRASOPORA BIMULATRIX Ulr 245 



1 and 6. Vertical and tangential sections, xis, of a specimen of the var. orientalis from 



Trenton Falls, N. Y. 



2 and 7. Similar sections of a Canadian (Ottawa) example of the same variety. 



3 and 8. Similar sections of a Kentucky specimen of the western or typical form of the 



species. 



4 and 9. Vertical and tangential sections of a specimen from the lower part of the Galena 



limestone at Mantorville. Minn. Mus. Reg. No. 5986. 



5 and 10. Similar sections of another example of the typical form of the species from the 



upper third of the Trenton shales at St. Paul. 



Figs. 11 to 15. PRASOPORA CONOIDEA Ulr 249 



11 to 13. Lateral, basal, and one sectional view of three specimens of this species, natural 

 size. 



14. Tangential section xis, showing the thin walls and minute acanthopores which are 



characteristic of the species. 



15. Vertical section, xis. The abundant tabulation of the tubes is the chief peculiarity 



brought out by this kind of section. 

 Upper third of the Trenton shales near Cannon Falls, Minn. 



Figs 16 and 17. PRASOPORA SELWYNI Nicholson .- 250 



16. Vertical section xis, showing the isolation and semi-circular form of the cystiphragms. 



17. Transverse section of same xis. 



Upper part of the Galena shales near Cannon Falls, Minn. 



Figs. 18 and 19. PRASOPORA INSULARIS, var. FILLMORENSIS, n. var 252 



- 18: A tangential section xis, showing the different appearance of the inter-zooecial spaces 

 when compared with typical P. insularis. 



19. Small portion of a vertical section xi8, showing the vesicular character of the inter- 



spaces to which is due the difference referred to in the preceding paragraph. 

 Probably from the Trenton shales near Fountain, Minn. 



Figs. 20 to 23. PRASOPORA INSULARIS, n. sp 251 



20. Tangential section of an excellently preserved specimen, xis. 



21. Small portion of same X50to show the minutely cellulose character of the walls. 



22. One zooecial tube with adjacent mesopores and one wall with adjoining cystiphragms 



and diaphragms, xi8. In showing the much greater abundance of the cystiphragms 

 and diaphragms when compared with other species of the genus, this figure, though 

 small, is sufficient for the identification of the present species. 



23. Small portion of another tangential section, x]8, in which the zooecial tubes are more 



frequently in contact than in fig. 20. 

 Galena shales near Cannon Falls, Minn. 



Figs. 24 to 26. PRASOPORA CONTIGUA Ulr 249 



24 and 25. Vertical and tangential sections, xis, of a specimen from the upper part of the 



Trenton shales of Goodhue county, Minn. 

 26. One zooecium and adjoining mesopores of same x35. Mus. Reg. No. 5989. 



