of the White Chalk of the Paris Basin. 395 



to the higher beds of the cretaceous group, the genera and 

 species of Foraminifers progressively increase, and that the 

 forms, at first very simple, analogous to those of oolitic tracts, 

 afterwards more complicated and specially appropriate to the 

 lower beds of the cretaceous system, have at last been replaced 

 in the upper parts by forms still more varied, the whole re- 

 curring in tertiary tracts, and even in the living state ; facts 

 which it has appeared to us important to establish in the hi- 

 story of Palaeontology. 



M. A. d'Orbigny then proceeds to describe the species of 

 Foraminifers found by him in the white chalk of the Paris 

 basin. The following is a list of them, together with their 

 localities : — 



liocalities. 



1. Nodosaria lirabata Meudon : very rare. 



2. Dentalina aculeata / Common at Sens : more rare at Meudon and in 



\ England. 



r Meudon : rare. Its analogue is found fossil in 

 3. communis < the Subapennine tracts of Italy and Austria, 



L ^"^ living in the Adriatic. 



4. gracilis At Sens and in England. 



- nodosa J Common at Sens, more rare at Meudon and 



\ St. Germain. 



f), Lorneiana Only in the environs of Sens. 



r Very common at Sens, Meudon, and St. Ger- 



m sulcata i ^"'*i"j ^"d in the chalk of England. Found 



j also in the green sand of the environs of 



L Mans (Sarthe). 



g r— multicostata ... i '^^"^' St. Germain : rare. Also at Maestricht 



' '*■ \ rarely. 



f Common at Sens, very rare at Meudon, St. 

 9. Marginulina trilobata < Germain, and in England: found only in 



|_ the young state. 



f Meudon : very rare. Occurs also in the green 



10. compressa j ^^^^ j^ ^^^ environs of Mans. 



r Common near Sens, very rare at Meudon and 



11. elongata < St. Germain. Occurs also in the chalk of 



I Ciply. 



12. gradata Only near Sens. 



13. raricosta Meudon: very rare. 



14. Frondicularia radiata Meudon and St. Germain: very rare. 



15. elegans Meudon and Sens: very rare. 



, „ v-.rr,«,.ii;ana J Commou at Sens, on the banks of the Yonne ; 



16- Verneuil.ana ... | ^^^^ ^^ g,^ Germain and Meudon. 



17. Archiaciana Meudon and Sens ; rare. 



18. ornata Found only once at Meudon. 



19. tricarinata Environs of Sens : seems to be rare. 



20. angulosa Meudon: very rare. 



21. Flabellina rugosa Sens and Meudon : common 



22. Baudouiniana Only at Sens. 



23. pulchra Meudon: very rare. 



r Very common in the white chalk of Meudon, 



24. Cristellaria rotulata < St. Germain, Sens, and in England. Occurs 



[ also in the green sand near Mans. 



25. navicula Sens and Meudon : rare. 



26. triangularis Sens: very rare. 



27. recta Meudon and St. Germain; rather rare. 



