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GEOLOGICAL MEMOIRS. 



ing the distinct geognostic horizon of the " brown Jura." The 

 whole mass consists of minute calcareous concretions like millet-seeds, 

 more or less round, and more or less firmly cemented together. 

 This rock, by its peculiar structure, its great development, its 

 colour, and. the great dearth of fossils, is everywhere easily recog- 

 nised. 



The Jurassic series of Swabia and Franconia, hitherto so perfect in 

 its members, is herein deficient. This purely pelagic formation 

 disappears eastward of the Black Forest, and here, as in north- 

 ern England, is entirely wanting. But on the west side of the 

 Black Forest, as soon as we descend into the valley of the Rhine, we 

 perceive northward of Lahr the steep mass, near Freiburg, forming 

 the Schoneberg, 2000 feet high. At Kandern we find also organic 

 remains (Echinidce and Terebratulce) . The Breisgau oolites are 

 connected with those of Switzerland through the Wartenberg, near 

 Basle, which latter often rise in high mountains. The whitish yellow 

 oolites contain but few fossils, and that only in the upper beds, where 

 Galerites depressus, Nucleolites scutatus, Disaster, Discoidea, Te- 

 rebrqtula varians, T. biplicata, T. spinosa, T. quadriplicate!,, &c, 

 are found. From Switzerland to Mont Jura, from thence to Bur- 

 gundy and the Haute Saone, and thence to the sea and beyond it, 

 the Great Oolite is nowhere wanting. Sometimes with trifling, 

 sometimes with great development, sometimes coarse, sometimes fine, 

 it produces everywhere the most excellent building-stone. Some- 

 times it forms extensive plains, as in Calvados, near Caen ; sometimes 

 steep mountains and deep rock-valleys, as in Burgundy and the Jura, 

 according to its greater horizontal or vertical development. In a 

 quarry in the plains of Caen, called carriere d' Allemagne, bones and 

 teeth of Fishes and Saurians frequently occur ; which correspond 

 perfectly to those of Stonesfield, near Oxford, where Fishes, Reptiles, 

 and the celebrated Bidelphys Prevostii have been found. In the 

 year 1831, Murchison wished to identify these Stonesfield oolites 

 with the beds at Solenhofen, but Voltz and v. Buch opposed this 

 view, in order to combat the Anglomania of the German geologists. 



Associated with the Great Oolite we generally find a compact, 

 greyish blue, marble-like limestone, called Forest-marble. No di- 

 stinct boundary between the two can be well made. In Mont Jura 

 and in Burgundy these deposits pass into one another, the oolitic 

 structure gradually making room for the compact, hard limestones. 

 Here this Forest Marble attains a great development. Similar to 

 the rude rock-masses of the " white Jura," which occupy the val- 

 leys of our Swabian Alps, the Forest-marble presents great rough 

 projections. Rent into clefts, as in our Alps, it forms caves and 

 grottoes, which are not inferior in beauty and size to those in Ger- 

 many. The cave of Arcy, between Avallon and Auxerre, penetrates 

 this rock. This formation, when greatly developed (Mont Jura, 

 Burgundy), contains no fossils, but abounds with them when its de- 

 velopment is less. The latter is the case in the west of France and 

 in the south of England. The extensive quarries near Ranville (two 

 leagues from Caen, near the Dives), disclose the beds belonging to 

 the Great Oolite division. The great freestones which are sent abroad 



