Dr. C. Struchmann — The Jura of Hanover and England. 551 



Kimmeridge, 10 species belong to the Lower Kimraeridge, while 

 2 species occur only in Upper Kimmeridge beds. 



From these comparisons it appears that the fauna of the Supra- 

 coralline beds is a mixed one, which unmistakeably shows close rela- 

 tions both with the Coralline Oolite and with the Lower Kimmeridge. 

 Nevertheless, the relations downwards, i.e. to the Coralline Oolite, 

 seem to me undoubtedly to preponderate. In this respect the Supra- 

 coralline beds occupy a position precisely similar to that of the 

 Upper Coralline Oolite (zone of Pecten varians) in the North-German 

 Upper Jura, so that I do not think I shall err in placing the two 

 parallel to one another. This notion certainly does not seem to be 

 quite in accordance with the opinion expressed by Waagen, who 

 regards the region of Ammonites alternans and Rhynchonella inconstaris 

 in the English Upper Jura as the equivalent of the Astartian, i.e. 

 of the Lower Kimmeridge ; but it appears from Blake's investiga- 

 tions that the two species do not at all belong to one and the same 

 zone, but that Ammonites alternans rather characterizes the Supra- 

 coralline beds, and Bhynchonella inconstans the Kimmeridge Passage- 

 beds, or the next higher zone. This, therefore, serves to explain 

 the apparent contradiction, the region of Rhynchonella inconstans 

 really corresponding to the Astartian, and all we have to do is to 

 separate the older stage with Ammonites alternans from the Kimmer- 

 idge and annex it to the Coralline Oolite as the uppermost stage. 

 * The occurrence of Ammonites alternans in the Supracoralline beds 

 (it is entirely wanting in the North-German Jura) cannot alone be a 

 reason for regarding the latter as of the same age as the zone of 

 Ammonites tenuilobatus, for the fauna of the Upper Jurassic forma- 

 tions in different districts teaches us how little dependence is 

 to be placed upon so-called characteristic fossils. Ostrea deltoidea 

 also offers an interesting example of this ; in England it appears 

 first in the Supracoralline beds, and then attains the climax of its 

 development in the Lower Kimmeridge. In the North-German Jura 

 I have recently determined the same species most definitely from 

 Hanover, Hoheneggelsen and Goslar ; but here it is exclusively con- 

 fined to the Coralline Oolite. (Ostrea Eoemeri, Quenst., which occurs 

 in the zone of Terebratida humeralis, is not, as D. Brauns sup- 

 poses, identical with 0. deltoidea.) On the other hand, Terehratula 

 subsella has hitherto been found in England only in the Supra- 

 coralline beds ; while in North Germany it extends up from the 

 Lower Kimmeridge into the Portland. I shall hereafter take the 

 opportunity of citing other similar examples. Consequently, I have 

 no hesitation in regarding the Supracoralline beds as equivalent to 

 the North-German Upper Coralline Oolite (i.e. the zone of Pecten 

 varians) , \\ie Wangen beds of Eastern Switzerland, the Rauracien 

 superieur of Western Switzerland, the Sequanien superieur of the 

 Haute-Marne (according to P. de Loriol), relatively, as the upper- 

 most horizon of the beds with Cidaris florigemma, and with 

 Ammonites himammatus (according to Waagen) and the Sequanien 

 inferieur of Boulogne-sur-Mer (according to P. de Loriol). 



5. The Kimmeridge Passage-beds according to our present know- 



