﻿FRAAS ON THE JURA FORMATION. 



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a decided transition to the Swabian Parkinsoni-clays. It is not, 

 therefore, altogether incorrect to parallel these strata. As to age 

 they seem to be the same, inasmuch as they everywhere underlie that 

 important geognostic horizon, the Callovien or the macrocephali- 

 bed. As far as I have examined the Jurassic series, I have never 

 found these strata of more than a few feet in thickness ; oolitic beds 

 from a reddish brown to a yellow colour are never absent, and these, 

 even if the lower beds deceive us, soon guide us again to the super- 

 incumbent ornati-cl&ys : and it is really astonishing to see in the 

 organic remains of foreign countries, for instance the " Brown-Jura" 

 fossils of the Himalaya and Cutch (Am. triplicatus, Am. macro- 

 cephalus, Am. Gowerianus, Trigonia costata, &c.) exactly the same 

 red-brown colour, as if the specimens had been collected from the 

 Kelloway of France or Germany. This bed of ferruginous oolite is 

 of very general occurrence ; — in the north of Germany, from the 

 Maine to the Rhine, from the Rhine to the Loire, in Calvados, and 

 in England : different typical shells, however, characterize the forma- 

 tion in the different countries. In France it abounds with Am. Par- 

 kinsoni, Terebratula varians, &c. ; and Am. macrocephalus, together 

 with Am. ornatus which lies above it, occur in a silicified state. On 

 the other hand, Am. macrocephalus of Swabia is here so constant that 

 it is never absent from this stratum even when but few feet thick. 

 In Switzerland, however, the fossils of the omati-ciajs already pass 

 down into these oolites. At the Balmberge near Solothurn, near 

 Bettlach, Valorbes, and the Bernese Jura, are found together with 

 the fossils of the macrocephali-bed (these Ammonites excepted), cal- 

 cified Am. ornatus, Am. annularis, Am. athleta, Am. convolutus, 

 which all re-appear in a silicified state in the black clays. With this 

 in France and England this formation commences. In Mont Jura and 

 in Burgundy (Chatillon-sur-Seine) the Callovien occurs in consider- 

 able force. The rock remains always the same. As characteristic 

 shells we have to notice Belem. latisulcatus, Am. anceps, Am. triplica- 

 tus, Am. Jason, Am. cordatus, and Terebr. biplicata. Here and there 

 Am. macrocephalus is also found in Mont Jura. The same obtains 

 in Calvados, near Dives, as also in England, namely, the shells of the 

 ornati-ciajs already appear here ; as, Am. Calloviensis (Jason), Am. 

 Duncani, Am. gemmatus (ornatus), Am. perarmatus, Am. athleta, 

 Am. bifrons (hecticus), Am. Konigii, Am. funiferus (Lamberti), Am. 

 sublcevis, and Am. macrocephalus. Near Chippenham is also found 

 Crioceratites Parkinsovii (Hamites bifurcati), [Ancyloceras Callo- 

 viense ?] which in Swabia occurs lower down in the series. 



If, however, the ferruginous oolites are palseontologically separable 

 into a German and a French-English series, the formations of these 

 countries unite again in the or^^-clays, the Oxford-clay, and the 

 black unctuous clays with silicified shells. Am. ornatus, Am. Jason, 

 Am. annularis , Am. caprinus, Am. convolutus, Am. bipartitus, Am. 

 hecticus, Am. Lamberti, are found in them in the German Jura, but 

 not all together at every locality. Already in Swabia are local dif- 

 ferences with regard to the shells distinctly perceivable. Am. orna- 

 tus and Am. bipartitus occur principally between Neuffen and 

 Lochen; they are also found singly at other places, but never in 



