PLATE XXV. 



PAGE. 



Figs. 1 to 11. BATOSTOMA FERTILE Ulr 290 



1 and 2. A small and a large specimen. 



3. Surface of the larger specimen, which is a typical example of the species, *9. 



4. Tangential section, prepared from the same specimen, xis. 

 5 and 6. Surface of the var. circulare xg and xis. 



7. Tangential section of a specimen with very thin walls and exceedingly small acantho- 



poreSj xis. The shaded spaces are mesopores. 

 8 and 9. Tangential sections of two specimens of the var. circulare, xis, the first with very 



thick wall, the second with them thinner and in this respect agreeing with figs. 5 and 6. 



10. Portion of the axial region of a transverse section of a typical specimen, *18. 



11. Vertical section of the natural size and a portion of same xi8; typical. 

 Lower third of the Trenton shales, Minneapolis. 



Figs. 12 to 15. BATOSTOMA MAGNOPOKA, n. sp 291 



12. A rather small specimen of the natural size. 



13. Tangential section xis. 



14. Part of the axial region of a transverse section xis. 



15. Vertical section xg. 



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



Figs. 16 to 25. BATOSTOMA VAKIUM, n. sp 292 



16 to 22. Seven figures illustrating the extreme variability displayed by tangential sections 



of this species; xis. Figs. 16 and 17 represent different parts of the same section, 18 



shows the tubes just after bending out of the axial region, 16, 19 and 20 are of common 



occurrence, and 21 and 22 show extremes rarely met with. 

 23 and 24. Halves of two vertical sections xg, the first normal, the second indicating some 



disturbance in the development of the tubes. 



25. One zooecial tube of a vertical section of the basal expansion xis. 

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



Figs. 26 to 28. BATOSTOMA MONTUOSUM, n. sp 293 



26. An average specimen of the natural size. 



27 and 28. Surface of a specimen with numerous closed mesopores xg and a small portion of 

 same xis. In many specimens the interspaces are narrower than is shown in these 

 figures. 

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



Figs. 29 to 36. BATOSTOMA HUMILE, n. sp 294 



29 to 31. Three fragments of the natural size. 



32. Small portion of a tangential section xis, of a specimen having a surface like fig. 34. 



33. Tangential section of a less matured example xis. 



34. Surface of an average fully matured example xg. 



35. Surface of a young example (corresponds to the lower part of flg. 33) xis. 



36. Surface of a fragment regarded as illustating a condition of extreme age, xis. 

 Galena shales near Cannon Falls, Minn. 



