PLATE XXVI. 



Pagh 



Figs. ] to 6. Bythopoea. heericki Ulr ^^' 



1. Vertical section x]8. showing slight Irregularity in the growth. 



2 and 3. Tangential section xi8 and a portion of same x50. ' 



4 and 5. A large and an average sized specimen. 



6. Surface of the smaller X9. 



Middle third of the Trenton shales at Minneapolis. 



Figs. 7 to 9. Bythopoka alcicoknis, n. sp ^' 



7 and 8. Two specimens of the natural size. 

 9. Surface of the larger one X9. 



Upper third of the Trenton shales near Cannon Falls. 



Figs. 10 to 16. HOMOTBYPELLA f?J SUBGRACILIS, n. Sp 23l 



10 and 11. Two tangential sections xi8, showing slight differences. 



12. Vertical section X 18.. The structure is almost entirely destroyed and only the direc- 

 tion of the tubes is to be made out with any certainty. 

 13 and 14. Two specimens, the second a little above the average in size. 

 15 and 16. Surface of the larger specimen xg and xi8. 

 Middle third of the Trenton shales, St. Paul. 



Figs. 17 to 19. Ebidotrypa bxigua, n. sp 26 



■ 17. A group of fragments as they appear mounted on a slide. 

 18 and 19, Two of them xg. 



Upper part of the Galena shales near Cannon Falls. 



Figs. 20, 21, 29 and 30. Eridotrypa mutabflis, var. minor, n. var 26 



20. Three fragments of the natural size. 



21. Surface of one of them ^9. 



29 and 30. Vertical and tangential sections xi8. 

 Galena shales near Cannon Falls. 



Figs. 22 to 28, 31, 32. Eridotry'pa mutabilis, n. sp 26 



22. A specimen of the average size. 



23. Large example . 



24. Surface of an old example presenting an unusual appearance, xi8. 



25. Surface of the original of flg. 23, x]8. The figure includes one of the maculae and ex- 



hibits the most common appearance of these. 



26 and 27. Tangential section xi8 and a portion of same X50 ; represents an average fully 

 matured condition. 



28. Vertical section of the same specimen xi8; shows a superficial layer of zooecia growing 

 in a direction opposite to the first set. 



31 and 32. Vertical and tangential sections xi8, of an» old specimen which has grown irreg- 

 ularly causing many interspaces and thus unusually numerous and large mesopores. 

 Galena shales, Goodhue county, Minn. 



Figs 33 to 37. Batostoma winchblli Ulr 2i 



33. A specimen of the usual diameter. 



34. Another, of large though not uncommon size. 



35. An average example of the var. nodosa. 



36. Surface of a fully matured example xg. 



37. Surface of the original of fig. 33 xg and xi8. (See also plate 27.) 

 Middle third of the Trenton shales, Minneapolis and St. Paul. 



Figs. 38 to 40, Batostoma minnbsotbnse, n. sp 2 



38 and 39. Two specimens, the first small, the other of the average size. 

 40. Surface of the larger specimen, which is in an excellent state of preservation, xg, show- 

 ing the granulose walls. (See also plate 27.) 

 Middle third of the Trenton shales, Minneapolis. 



