The C6te~d' Or, France, and the Cotteswold ElUIs. 571 



have to be substituted in correlating distant beds. In France, Ger- 

 many, and Switzerland, the beds admit of a triple division. The 

 first, in descending order, characterized by numerous species of 

 Nerincea and Diceras arietina, is termed the " Nerinsean zone ; " the 

 second, remarkable for the large number of corals it contains, the 

 " Coral zone ; " and the third is called the " Echinidian zone," from 

 the abundance of Echinoderms in it. Of these three zones the 

 Coralline Oolite, Coral Eag, and Pisolite, of William Smith, may, in 

 Dr. Wright's opinion, be correlated with the second and third zones 

 just mentioned. The newest or Nerinaean zone is absent in England, 

 and this forms a distinct group, according to M. Martin, to which he 

 gives the name SSquanien, while he applies the term Gorallien to the 

 other beds just below it, and which lie above the Oxfordien. 



7. KiMMERiDGE Clat. — The Upper Jurassic rocks were found by 

 Dr. Wright to present a greater diversity of character in different 

 regions than the members of the middle and lower divisions : the 

 difficulty of establishing the synchronism of their several stages 

 increases in the ascent from the Coral Eag to the summit of the 

 Purbeck series. Our chief obstacle is considered by him to be the 

 want of a better classification, and a more detailed study of the 

 Kimmeridge Clay, and Portland formations of England, M. Martin 

 divides his Kimmeridien into — 1. Marls and compact limestones with 

 Ostrea virgula. 2. Calcairesd Pteroceren with Ostrea virgula sparingly. 



8. Portland Beds. — M. Martin makes two divisions of these 

 beds, which are composed of marly limestones, the upper with Tri- 

 gonia Boloniensis and Pinna supra-j'urensis ; the lower with Am- 

 monites gigas. Dr. "Wright points out the divisions made by other 

 geologists. It is, however, in the environs of Boulogne-sur-Mer that 

 perhaps the beds are best studied, and he therefore devotes some 

 attention to the section given by M. Pellat. This he gives in a con- 

 densed form. The Portland beds are here divided into an Upper, 

 Middle, and Lower, and comparing them with the section at Hart- 

 well, he comes to these conclusions — 1st. That in England the Lower 

 Portlandien, or the beds with Perna rugosa and Pterocera Oceani, is 

 absent. 2nd. That the Middle Portlandien is represented by the 

 dark sandy clays of the brick-yard at Hartwell, containing Ammonites 

 hiplex, Cardium Morinicum, and Ostrea expansa, etc. A portion, like- 

 wise, of the overlying fossiliferous sand, with green Grlauconitic 

 grains, belongs to this group. 3rd. The Upper Portlandien, so 

 largely developed in England, has at its base the non-fossiliferous 

 sands without Griauconite, and in its middle and upper portions the 

 true calcareo- siliceous limestones and other beds forming the Port- 

 land stone. 



The correlation of our English strata with others at a distance is a 

 subject of the highest interest, and although this sketch does little 

 justice to Dr. Wright's elaborate paper, our object is gained by 

 bringing it under the notice of the readers of the Geological 

 Magazine. — H.B.W. 



