of the White Chalk of the Pqiris Basin. 39? 



Of the fifty- four species, seven occur also in lower or higher 

 beds: thus in the green sand of Mans are found three spe- 

 cies, Dentalina sulcata^ Marginulina compressa, and Cristel^ 

 laria roiulata ; in the coral chalk of Tours, which is higher 

 in position than the white chalk, two species, Bulimina obtusa 

 and Textularia turris-, and in the chalk of Maestricht, being 

 the highest in position, two species, Dentalina multicostata 

 and Rotalina Cordieriana. We also find two species, the 

 analogues of which occur both fossil in the tertiary tracts of 

 Austria and Italy, and in the living state in the Adriatic, 

 namel}^, Dentalina communis and Rotalina umhilicata. With 

 these exceptions there still remoAn forty -seven species peculiar 

 to the white chalk, showing clearly that it forms a bed distinct 

 from all the rest of the cretaceous system, belonging to a small 

 local fauna well-defined. 



On comparing the above genera given by M. d'Orbigny 

 with those named by Dr. Ehrenberg in his tabular view of 

 the Bryozoa, inserted in the early part of this paper, it will 

 be seen that Nodosaria, Dentalina, Marginulina, Frondicu- 

 laria are included in the family of the Nodosarina of the latter 

 author; Cristellaria, Rotalina, Truncatulina, included in his 

 family of the Rotalina; Globigerina, Rosalina, Valvulina, 

 Bulimina, Uvigerina, Pyrulina, in his family of the Uvellina; 

 and Textularia in his family of the Textularina. The Lituola 

 nautiloidea of Lamarck and d'Orbigny is the Coscinospira 

 nautiloides of Ehrenberg, included in the Fabularina family 

 of the latter. 



If we now, observes M. d'Orbigny, compare the fauna of the 

 Foraminifers of the white chalk with those of different seas, 

 with a view of determining the analogy of composition, and of 

 obtaining data respecting the temperature of that basin at the 

 time when these species lived, we shall find this analogy more 

 striking in the Adriatic Sea than anywhere else. There only, 

 the same as in the chalk, are found in abundance Nodosaria, 

 Dentalina, Marginulina, Frondicularia; there only occur a 

 considerable number of species of Bulimina. This sea alone 

 in the present day contains living Frondicularia; of Fron- 

 dicularia so varied in the white chalk; and, to complete 

 the approximation, it exhibits to us the only two living spe- 

 cies, the analogues of which are found in the fossil state in the 

 white chalk, namely, Dentalina communis and Rotalina um- 

 bilicata. This analogy of zoological forms would lead us to 

 believe, 1st, that the basin in which is deposited the white 

 chalk of Paris was subject to a warm temperature; 2nd, that 

 it was circumscribed, protected from waves and from every 

 violent current proceeding from a distance, since the bodies 



