PLATE XXVIl. 



Page 



Figs. 1 to 8. Batostoma winchelm Ulr ^'" 



1, 2 and 3. Vertical sections xi8, of a young, medium, and an old specimen. 



4 and 5. Tangential section, xi8 and x50, of the same specimen from which was prepared 



the vertical section shown in flg. 3. 

 6. Tangential section of a young specimen xi8. 



7 and. 8. Tangential section of the var spmidosum xi8 and x50. (See also plate 26.) 

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



Figs. 9 to 15. Batostoma minnesotbnse, n. sp ■■ 2^' 



9 and iO. Portions of a tangential section xig and x50. 



11 and 12. Peripheral and axial regions of a vertical section prepared from the same speci- 

 men as the preceding, x]8. 

 13. The peripheral part of a zocScial tube with fewer diaphragms than usual, xi8. The true 



average for the species is intermediate between this and flg. 11. 

 14 and 15. Portions of two tangential sections, xi8 and x50, in a different state of preser- 

 vation than flgs. 9 and 10. (See also plate 26.) 

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



Figs. 16 to 19. Batostoma (?) dbcipiens, n. sp 29! 



16. Small portion of a vertical section xi8. 



17 and 18. Tangential section xi8 and x,50. In some parts of this section certain small 



acanthopore-like dots are distinguishable usually about midway between the angles. 



They are dark and scarcely half the size of the smallest shown in flg. 10. 



19. From the axial region of a transverse section xi8. 

 Lower half of the Trenton shale?, Minneapolis. 



Figs. 20 and 21 . Leptotbtpa claviformis, n. sp 31! 



20. Tangential section xt8. In this section the cells here drawn as open are filled with 



matrix, while those shaded are occupied by clear calclte. The smaller of the latter 

 have the appearance of mesopores; on the other hand, since the preservation of the 

 fossil is not favorable, it is possible that they represent acanthopores. 



21. Vertical section of the upper extremity of same beyond the foreign body, xi8. 

 Middle third of the Trenton shales, St. Paul. 



Figs. 22 and 23. Lbptotkypa infoemis, n. sp 31' 



Tangential and vertical sections xis. 



Lower third of the Trenton shales, Minneapolis. 



Figs. 24 and 25. Lbptotkypa acervulosa, n. sp 31 



Tangential and vertical sections xi8. 

 Galena shales, Decorah, Iowa. 



Figs. 26 and 27. Moitotrypa (?Oh^tetes) cfmulata, n. sp 30 



Tangential and vertical sections xg. Beneath the first the structure of the wall is shown X35. 

 Upper part of the Galena shales, Goodhue county, Minn. 



Figs. 28 and 29. Mokotbypa magna, n. sp 30 



Vertical and tangential sections xg. 



"Lower Blue" limestone at Dixon, 111. 



