PLATE XVI 
Kies: 1t010-: VERASOPORALSUM Ul ACU Tex UDI e5s )olinlo sls io.o over aiarels)s\o/alejcreie ots talalstolaleeteisvaists oleritareret aisieteistersieiee 
land6. Vertical and tangential sections, X18, of a specimen of the var. orientalis from 
Trenton Falls, N. Y. 
2and7. Similar sections of a Canadian (Ottawa) example of the same variety. 
3and8. Similar sections of a Kentucky specimen of the western or typical form of the 
species. 
4and9. 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. 
Bigs pllsbOnlbs eR ASO POH Al CON OLDIE AGU crtter ete reretetaeteyofeastatsleteleretstavenareleinystereretst= aveleilep=ialaletoietaie stele stae tel tater 
11 to 13. Lateral, basal, and one sectional view of three specimens of this species, natural 
size. 
14. Tangential section <18, showing the thin walls and minute acanthopores which are 
characteristic of the species. 
15. Vertical section, X18. 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. 
Wigs Gand ieee PRASOLORAVSEL WAYNE @ NICH OLS Ol tiereiaxelalcttalells ce oie oreo aie eicieisioieieians(-feinietstetere ist eteieicie tetera 
16. Vertical section X18, showing the isolation and semi-circular form of the cystiphragms. 
17. Transverse section of same X18. 
Upper part of the Galena shales near Cannon Falls, Minn. 
Figs. 18 and 19, PRASOPORA INSULARIS, Var. FILLMORENSITS, 1. Val......--cc+cececsceeccee ceseee 
18. A tangential section X18, showing the different appearance of the ateenoeaat spaces 
when compared with typical P. insularis. 
19. Small portion of a vertical section 18, 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: 
Higsy 20to 2a CE RASOPORAGIN SUM ARIS, pM eg SP iraiarercrareteleyateiataterteyotetenetsteleta ofeie tale feheyete efenmnrerellcpeistaul-ie\eleletefetetstelste 
20. Tangential section of an excellently preserved specimen, X18. 
21. Small portion of same 50 to show the minutely cellulose character of the walls. 
22. One zocecial tube with adjacent mesopores and one wall with adjoining cystiphragms 
and diaphragms, 18. 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, x18, in which the zoccial tubes are more 
frequently in contact than in fig. 20. 
Galena shales near Cannon Falls, Minn. 
Bigs. 24 to:26-— PRASOPORAS CONIDEG UA Wilyayercretetate eievepeislori=lajelaleicleisy in1s/<ie1s!clerieialelniele\«lstelloie/ale>=elaleiel=tall[nicteta[= 5 
24 and 25. Vertical and tangential sections, 18, of a specimen from the upper part of the 
Trenton shales of Goodhue county, Minn. 
26. One zocecium and adjoining mesopores of same x35, Mus. Reg. No. 5989. 
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249 
