﻿74 



GEOLOGICAL MEMOIRS. 



sent in the North of England, and nowhere repeated on the Continent. 

 The North-German " Jura "-formations of the Langenberg, and the 

 above-mentioned limestones of France and Switzerland have certainly 

 been termed " Portland," and attempts have even been made to apply 

 this name to the Swabian and Franconian calcareous beds ; but this 

 general use of the term is quite erroneous ; for there exists not the least 

 similarity either in a mineralogical or a paloeontological point of view 

 between the Portland-stone of England and the so-called " Portland" 

 of France, Germany, and Switzerland ; and it was only the somewhat 

 similar succession of the strata, or the natural feeling to apply to the 

 last bed of the " Jura" one and the same name, which led to this 

 misuse of the term " Portland." The Portland-stone is only a por- 

 tion of the great series of strata forming the Mo\\u.sc-facies of the 

 Upper " White Jura." 



3. The Vertebrate-facies. — The zoological succession now leads 

 us to the Group [Form] of the Upper "White Jura" in which Arti- 

 culata and Vertehrata appear. Crustacea and Fishes here play the 

 principal part. The only representatives of the Molluscs are the 

 Cephalopods. But geognostically this Facies is connected with the 

 first, the Coral-facies ; because this higher Fauna has been developed 

 only in bays and creeks protected by Coral-reefs. Only at the bottom 

 of the most tranquil seas could such laminated beds, as the valuable 

 Lithographic Shales, have been formed of the finest calcareous mud. 

 Between the Randen near SchafFhausen and the "Jura" heights 

 near Ratisbon, at the side of the great Coral-reef which extends 

 N.W. and S.E., and above the massive Marbles and Dolomites, lie 

 a series of calcareous beds, of finer or coarser grain, in smooth thin 

 laminse or in much thicker slabs. In Swabia these beds are much 

 coarser, intersected with calc-spar veins, not splitting regularly, and 

 alternating with clays ; but the Franconian beds are of a much finer 

 substance, more homogeneous and harder ; they are, however, easily 

 distinguishable at both places from the other Jurassic rocks by the 

 clear sound they give when struck with a hammer. Only the Fran- 

 conian slates are used for lithographic purposes, the most celebrated 

 being those of Solenhofen and Mernsheim ; attempts have also been 

 made to* use the Swabian schists for this purpose, but without success. 

 The juxtaposition of these laminated beds with the Coral-rag may 

 be observed at many places ; and we often see the reef-like rocks, 

 isolated, in groups, or in rows, projecting above the horizontal shales. 

 Thus, the Herdtfeld consists of a large basin everywhere surrounded 

 by reefs of Coral-rag. At Solenhofen and Mernsheim, we can see 

 that the shales lie lower than the projections, and yet above the 

 mass, of the Dolomites. Near the Mernsheim ruins, we see, upon 

 the summit, rocks with Terebrat. inconstans and T. trilobata ; at the 

 side and below are the lithographic slate quarries, penetrating into 

 the rock. Near Kelheim, Ran deck, and Kelheimwinzer the Biceras- 

 limestones so clearly pass into the Fish-slates, that no doubt can exist 

 that the two beds lie side by side. The laminated beds here pene- 

 trate into the Limestone or the Dolomite, or they alternate one with 

 another. 



The remains of animals of higher orders occur in this slate \ Fishes, 



