IO 



NORTH AMERICAN INDEX FOSSILS. 



increasing in size. Aperture usually an arched slit at the base of 

 the inner wall of the last chamber. Carbonic-Recent. 



4. T. globulosa Ehr. (Fig. 10.) Cret.-Re- 

 cent. 5. T. (Verneuilina) triquetra 

 (Munst). (Fig. 11.) Cret.-Recent. 



NODOSARIA. 



Chambers in a single row, smooth or or- 

 namented. Siluric (?)-Recent. 



6. N. communis (d'Orb.). 



Fig. 10. Textularia 



(Fig. I2#.) 8 lobulosa ( Minn - Geo1 - 

 _ P Surv.), much enlarged. 



Perm -Recent. 7. N. bacillum Defrance. 



(Fig. 12b.) Eocenic. 8. N. zippei, Reuss (Fig. 12c.) Cretacic. 



V. Orbulina d'Orbigny. 

 Shell a simple sphere with a large oral 

 opening and numerous foramina. (Cambric ?) 

 Trias-Recent. 

 9. 0. universa d'Orb. (Fig. 13.) Trias-Recent. 



FlG. 12. a, Nodosaria 

 communis; b, N. bacil- 

 lum; c, N. zippei (a-b, 

 Md. Geol. Surv. ; c, 

 Bagg), greatly enlarged. 



Fig. 13. Orbulina universa. 

 FlG. 14. Globigerina bul- 

 loides (Minn. Geol. Surv.), 

 much enlarged. 



FlG. 16. Truncatulina 

 lobatula (Md. Geol. 

 Surv.), enlarged. 



VI. Globigerina d'Orbigny. 



Free, calcareous, perforated by coarse tubules. Composed of 

 several globular chambers, which are irregularly arranged or in an 

 imperfect spiral. (Cambric?) Trias- 

 sic-Recent. 

 10. G. bulloides d'Orb. (Fig. 14.) 



Cret.-Recent. 



Globigerina, Textularia, etc., are very 

 abundant in the American chalk (Ni- 

 obrara) and also in the Atlantic and ( a f ter 

 Gulf Tertiary. larged. 



17. Endothyra bailey i 

 Whitfield), much en- 



