Davidson — On Continental Geology. 



205 



Subdivisions of the Cretaceous System. (By M. E. Eenevier.) 



Danien = Upper Chalk of Maestricht : Limestone witli Baculites : 



Super- 

 Cretaceous 



Group 



or 



Senonien. 



Meso- 



Cretaceous 



or 



Cenomanien. 



Infer- 



Cretaceous 



or 

 Neocomien. 



(Pisolifcic Limestone ; occurs neither in Switzerland nor England). 

 Senonien =. White Chalk : Chalk with flints : Chalk of Meudon : 



Upper Chalk, Norwich, Gravesend, Woolwich, in England ; 



Seewerkalk, in Switzerland. 

 Santonien = Lower Senonien, Chalk of Villedieu, (peculiar to 



Prance, and does not occur either in Switzerland or Great Britain). 

 ''Turonien ^ Craie tufFeau ; Chalk with Inoceramus mytiloides . (Upper 



portion of Lower Chalk of Beaehy Head in England, does not 



occur in Switzerland). 

 Carentonien = Upper portion of the Green Sands of the Sarthe ; 



(zone with Ostrea biauriculata does not occur either in England or 



Switzerland). 

 Hotomagien = Craie Marneuse ; Chalk of Rouen : Lower part of 



Lmver Chalk Ventnor : Chlor. Marl England. Cheville and St. 



Croix in Switzerland. 

 Vraconnien^Upper Green Sand : zone with Pecten asper : Upper 



Gault in Switzerland, Cheville, St. Croix, Perte du Rhone : War- 

 minster and Cambridge in England. 

 Albien ^ Gault. Middle and Lower Gault in Switzerland (Cheville, 

 (^ Perte du Rhone, St. Croix, etc.). Folkestone, Wellant, etc. 

 "Aptien = Clay with Plicatulm: Upper Aptien : Hai-d Sandstone of the 



Perte du Rhone : upper portion of Lower Green Sand of England. 

 Rhodauien = Lower Aptien, Yellow Marls of the Perte du Rhone, 



red bed of Vassy ; lower portion of Lower Green Sand of England, 



Perna bed of the Crackers of Die. Lonsdalii. 

 Urgonien = Upper Neocomien : White Limestone with Req. Ammonia, 



1 : Zone of Rudistes : Yellow Limestone of Maurmont, Russille. 

 Neocomien = Middle Neocomien ; Maries of Hauterive : Limestone 



with Spatangus : Yellow Limestone of Neuchatel : Mortean 



Marie of Hauterive : Yellow Marie oi Am. Astierianus. 

 Valangien := Lower Neocomien : zone with Pygurus rostratus : Lime- 

 stone of Berrias ? 



In a paper, by the same author, published in the Bulletin of 

 the Societe Vaudoise of Natural History, vol. v. p. 51, it is stated 

 that the Lower Green Sand does not equal (as the larger number of 

 geologists have supposed) the Neocomien, but would exactly corre- 

 spond to the Aptien beds, which he (M. Eenevier), recognised be- 

 tween the Upper Neocomien (Urgonien) and the Gault. That the 

 lower beds of the Lower Green Sand (Perna beds and Crackers of 

 the Isle of Wight) contain a fauna which is analogous to that of the 

 Lower Aptien (Rhodanien) of the Perte-du-Ehone, while the are- 

 naceous bed of about 650 English feet, situated between The Crackers 

 and the Gault, belongs without doubt, to the Aptien ; and in concluding 

 his memoir on the " Faune de Cheville," M. Eenevier hesitates to 

 admit as large a number of divisions in the Cretaceous system as 

 have been proi^osed by M. Coquand, but at the same time he considers 

 that each fauna, of which the larger number of species are peculiar 

 to it, and not offering a mere local aspect, but occupying a rather 

 general stratigraphical horizon, should constitute an independent 

 division. He in consequence willingly admits all the divisions 

 recently introduced partaking of those conditions, and all those of 

 which the Palaeontological monographs will in future demonstrate 

 their utility. 



{To be continmd). 



