PLATE XXI. 



PAGE. 



FigS. 1 to 7. COXSTELLARIA VAKIA, n. sp 311 



1. Surface of a mature example, *9, with wide interspaces aud correspondingly narrow 



zcKECial apertures. 



2. Surface, xis, of another example showing a less matured stage than flg. 1, the inter- 



spaces being thinner and the zocecial apertures larger. 



3. Tangential section, xis, showing appearances immediately beneath the surface of an old 



specimen. At deeper levels the walls are thinner and the interspaces narrower. 



4. Small portion of preceding, xso, with two of the minute mural tubuli. 



5. Vertical section of an average specimen, xig. 



6 and 7. Two fragments of the natural size, one very small, the other of medium dimen- 

 sions. 

 Galena shales near Cannon Falls, Minn. 



FigS. 8 to 12. NlCHOLSONELLA PULCHBA, n. Sp 314 



8. An unusually wide fragment of the natural size. 



9. Surface of same, xg. 



10. Two portions of a tangential section, xis, the upper illustrating the appearance just 



beneath the surface of a mature example, the lower at a deeper level. 



11. Vertical section of same, xi8. 



12. Central portion of a transverse section, xis. 

 "Pierce limestone", Murfreesboro, Tenn. 



Figs. 13, 14, 20 and 22. NICHOLSONELLA PONDEROSA ? Ulrich 316 



13. Two portions of a tangential section, xis. In the original the details are obscure and 



it is probable that the interstitial dots are too numerous and small. 



20. Small portion of the peripheral part of a vertical section, xis. The structure is but 



illy preserved in these sections. 



14. Two portions of a tangential section of another specimen, xis, the upper immediately 



beneath the surface. 



22. From the peripheral part of a transverse section of same, xis. 

 Lower third of the Trenton shales, Minneapolis. 



Figs. 15 to 19 and 21. NICHOLSONELLA LAMIKATA, n. sp 315 



15. Tangential section of specimen in an unusually good state of preservation, xi8. 

 16 and 17. Portions of same X50. 



18 and 19. Under side of a fragment, nat. size, and the upper surface xg. In this specimen 

 the mesopores are shown much more clearly than in others. 



21. Small portion of a vertical section, xis, passing through one of the maculae. 

 Middle third of the Trenton shales, Minneapolis. 



Figs. 23 to 40. TREMATOPOBA ? PRIMIGENIA (and varieties) Ulrich 309 



23 to 27. Fragments of the typical form. 

 28 and 33. Original type of T. ornata and surface of same xis. 



29. A large specimen of var. spinosa ; 30, a smaller and better preserved fragment; 35, sur- 

 face of the latter, xg; 35, small portion of same xi8. 



31. Surface, xg, of an average example of the typical form. No attempt has been made to 



draw the small acanthopores. 



32. Surface of specimen with acanthopores unusually abundant and inflecting the zooacial 



apertures, xis. The specimen is peculiar also in having many of the mesopores open. 

 34. Original of flg. 26, xis, (var. ornata) with spines and occasional open pores in the inter 

 spaces. 



37. Tangential section, xis, from a specimen whose surface is drawn in flg. 32. 



38. More common appearance of typical tangential sections, xis. 



39. Small part of preceding x50. 



40. Vertical section of basal expansion, xis. It is attached to a crinoid column and shows 



how the tubes grew into the depressions between the rings and failed to attain ma- 

 turity. 

 Middle third of the.Trenton shales, Minneapolis. 



