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GEOLOGICAL MEMOIRS. 



with the upper marly beds of y, which contain, like those in France, 

 fragments of Myce and Cidarites. Corals can never be regarded 

 as typical forms in different countries, for, according to climatal 

 conditions, a bed may contain corals at one place and be destitute 

 of them at another. Corals have even been found in Swabia in y, in 

 the stone-quarries at Donzdorf, at the foot of the Hohenzollern, and at 

 other places. This occurrence of corals in the "brown Jura," which, 

 commencing in the eastern Jura-range of France, stretches into Bur- 

 gundy, and from thence into the English Inferior Oolite, is again a 

 proof how every stratum can become a coral-rag, and how the whole 

 fades of a bed may be subject to variations even under similar exist- 

 ing conditions. Already connected with this is the succeeding Great 

 Oolite, so important a formation both in England and France, which 

 is associated, above with the Forest-marble, and below with the Lse- 

 donian limestone. In these three formations is centred the whole 

 French Jura-elevation ; here are the highest summits and the greatest 

 extensions in width ; and it is only the clays that are interstratified 

 with it, often unobserved and of insignificant thickness, that faintly 

 remind us of the parallels in other countries. 



To these limestones first succeed the calcareous marls, light grey 

 or blue, with badly preserved fragments of Ammonites and Belem- 

 nites, but rich in Conchifera. I do not hesitate to regard the Marnes 

 vesuliennes or Fuller' s-earth as the equivalent of our d. Am. coro- 

 natus and Bel. giganieus are certainly wanting, but the mass of the 

 shells resemble those in Swabia. These marls are properly charac- 

 terized by Ostrea Marshii (crista-galli), 0. Knorri, O. acuminata, 

 Gervillia, Perna, Pholadomya Vezlayi, Pleuromya, Nucleolites, and 

 Bysaster. In Burgundy, where the limestones are in greater force 

 than the clays, hard yellow limestones, termed Oolite inferieure, with 

 Am. Parkinsoni and Bonax Alduini, for the most part take the place 

 of the clays ; but there are generally found a few clay beds on the top, 

 with Gervillice and Pernae, which the geologists of that district call 

 Marnes afoulon. These clays reappear particularly in theDeparte- 

 ment de la Sarthe, where the two last-mentioned shells, together with 

 Gervillia tortuosa and Gastrochcena, are numerous and well-preserved. 



To this also is the English formation related. The y. is either 

 referable to " inferior oolite," or rather it is not to be distinguished 

 as a special bed. Still there are sandstones that pass into oolitic 

 limestone with Pentacrinites vulgaris, Terebratulce, and Corals. 

 Above these in the south of England occur the beds of Fuller' s- 

 earth, sometimes argillaceous, sometimes arenaceous, in which Ger- 

 villia, Perna, Pinna, Ostrea acuminata, Modiola gibbosa, JJnio 

 abductus, Mya, Isocardia striata, I. concentrica, Pleurotomaria, 

 and Terebratulce, are found in great numbers. In the north of 

 England (Carlton Bank, Yorkshire) the lower coal or lower Moor- 

 land sandstone, according to Murchison, consists of a great, local 

 sandstone formation, with a large quantity of fragments of plants, 

 which is placed between the inferior oolite and the grey "lime- 

 stone" of Phillips. But the grey limestone of Yorkshire is merely 

 what the Fuller' s-earth of the south, the Marnes a foulon, and the 

 Marnes vesuliennes also are, the h. of the Swabian " brown Jura." 



