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GEOLOGICAL MEMOIRS. 



cylindrical Astraia helianthoides, A. alveolata, A. tubulifera; Cida- 

 rites coronatus (florigemma), Echinus germinans, Clypeus emargi- 

 natus, Spatangus ovalis ; Apiocrinites Milleri, A. subpentagonalis ; 

 Trochis ; Turbo; Nerincea ; Am. inflatus, Am. perarmatus, and Am. 

 planulati. The third division of the Coral-rag forms the Upper Cal- 

 careous Grit, which is not, however, found everywhere ; this, like the 

 Lower Grit, is characterized by a quantity of small Bivalves and frag- 

 ments of shells. The same obtains in Normandy, where near the 

 coast, between Caen and Honfleur, as also in the interior, near Li- 

 sieux in the Mortagne, the whitish-yellow oolite of the Coral-rag is 

 found in considerable extent, but in little force. Radiata in parti- 

 cular appear here, and a bed full of Trigonia clavellata separates this 

 formation from the Argiles de Dives. Here, as in the German 

 " Jura," the absence of Cephalopods, and the predominance of 

 Corals, Radiata, and Bivalves related to Ostrea form a well-marked 

 horizon ; in the German "Jura" the absence of all bedding and the 

 massive character of the formation clearly mark out the horizon and 

 that indeed the last in the "Jura," for henceforth the formations 

 undergo great variations, the examination of which is the most diffi- 

 cult of the whole Jurassic series. We have especially to guard 

 against any expectation of placing the beds of different localities in 

 any one order of succession ; so as to say, for instance, that Diceras- 

 limestones lie above or beneath the Solenhofen-slates or below the 

 Portland-oolite. These are, rather, three separate and peculiar 

 Forms, lying side by side. 



We may, perhaps, best comprehend the Divisions of the " Jura" 

 above the Coral-rag by the ensemble of the organic remains ; we will 

 therefore consider first the Corsl-facies, secondly the Mollusc-fades, 

 and thirdly the Y ertebrate-f acies. 



1. The Coral-facies. — The unstratified "White Jura" is not over- 

 laid by any more extensive bed, and forms the last member of the 

 Jurassic series. This is sometimes the case over wide tracts ; some- 

 times it only offers prominent isolated spots and ancient coral-reefs 

 and shores, in whose basins and creeks the younger, stratified Jurassic 

 rocks repose. 



In the Franconian " Jura "-range from Staff elstein toParsberg the 

 Dolomites are not overlaid by any other Jurassic bed ; for they are 

 everywhere covered with post-tertiary formations, often immense accu- 

 mulations of shingle-sands [Geschieb-Sande] (Hastings-sand?), above 

 which here and there on the dreary plateau projections of the Dolo- 

 mite appear, whilst the massive Dolomite is exposed in the valleys. 

 The same is the case upon the road from the Wisen Valley (Mug- 

 gendorf and Streitberg) to Amberg. And we find that the Dolomite 

 of the Heights, when broken, exhibits traces of Corals and Tere- 

 bratulce. Generally, however, isolated tracts and points only of this 

 rock occur, and these have often surrounded in extensive semicircles 

 the basins of the Jurassic beds, and afforded protection to the preci- 

 pitations of the fine mud that formed the Solenhofen-slates. Of such 

 spots the Swabian "Jura" presents a great number between the 

 Randen and the Bies, where we may observe the unstratified calcareous 

 masses lying side by side with the stratified Lobster-claw-shales ; the 



