556 B)'. C. Struckmann — The Jura of Hanover and England, 



cannot, therefore, considering their analogous conditions of stratifi- 

 cation, present any hindrance to our regarding them as contempo- 

 raneous deposits. In North Germany I have distinguished only two 

 subdivisions of the Portland, — the beds with Ammonites gigas, and 

 the Eimbeckhauser Plattenkalke ; but if the so-called Miinder 

 Mergel, which marks the transition to the Purbeck, ought also to 

 be referred to the Portland, and not to the Purbeck (a point which 

 I leave for the present undecided), we should have to distinguish 

 three zones in Hanover, just as in the Haute-Marne and near 

 Boulogne. If in England, contrary to what occurs in France, only 

 two great subdivisions can be distinguished, I regard this as an 

 accidental circumstance of quite subordinate importance, which 

 certainly does not justify the assumption that the lower part of the 

 French Portland formations was not deposited contemporaneously 

 with the English Portland, but with the Upper beds of the English 



Principal Groups 



OfthkWkalden and 



Upper Jurassic. 



Divisions in Enqladn. 



Divisions in Hanover. 



"Wealden. < 



a. Weald Clay. 



b. Hastings beds. 



c. Purbeck beds. 



Portland Stone. 

 Portland Sand. 



a. Weald Clay or Upper Wealden. 



b. Hastings Sandstone or Middle 



Wealden. 



c. Purbeck (Serpulite) or Lower 



Wealden. 



Portland. < 



Miinder-Mergel as transition be- 

 tween Purbeck and Portland. 

 Eimbeckhauser Plattenkalke. 

 Beds with Ammonites gigas. 



KiMMERIDGE. < 



I 



a. Upper Kimmeridge Clay. 



I. Lower Kimmeridge Clay. 



e. Kimmeridge Passage - 

 beds. 



a. Upper Kimmeridge or Fw-p'M^ff- 



beds. 



b. Middle Kimmeridge or Ftero- 



cews-beds. 



c. Lower Kimmeridge (Astartian), 



i.e. Nerinaa-heds and zone of 

 Terebratula humeralis. 



Coralline Oolite 

 (Corallian or Beds 

 ■with Cidaris Jtori-"^. 

 gemma). 



a. Supra-coralline beds 

 (Upper Calcareous Grit) . 



b. Coral Eag, Coralline 



Oolite and Middle Cal- 

 careous Grit. 



a. Upper Coralline Oolite (zone of 



Pecten vnrians). 



b. Lower Coralline Oolite (zone of 



Ostrea rastellaris and Coral- 

 bed). 



Oxford Group. •< 



a. Lower Limestone and 



Lower Calcareous Grit. 



b. Upper region of the 



Oxford Clay, with Am- 

 munites cordatus and 

 Ostrea dilatata. 



)■ Hersumer Beds. 



Kelloway Group | 

 OP THE Middle >( 

 Jura. 



Then follow :— 



a. Zone of Ammonites 



Jason. 



b. Zone of Ammonites 



macrocephalus. 



a. Ornatus-clays. 



b. Macroeephalus-heds. 



