of Local Influences upon the Formation of Strata. 113 



nosa, and T. nucleata* all characteristic of the ♦* white Jura.'* 

 Even if the sponge corals are wanting in the Alps, this must 

 not mislead us. Corals can never be characteristic of forma- 

 tions ; they appear, rather, everywhere, if climatal conditions 

 have been favourable ; and the spongites limestones of Ger- 

 many were only Sbnoiher fades of the sea, which in the south 

 of Europe has formed the alpine limestone. With this view, 

 the stratigraphical order of the other Jurassic formations 

 agrees ; for in Provence, below the alpine limestone, the 

 ornati clays with Am. Parkinsoni occur ; lower down the opa- 

 linus clays and the lias. This Jurassic group extends, in 

 France, from the Mediterranean, along the Cevennes and the 

 Alps, to Mont d'Or Lyonnais, and in the north of the Isere 

 Department, where the form of the English-French ** Jura" 

 commences. If, now, in the latter Jurassic range ** oolite*' 

 is pre-eminently developed, and in the north of Europe 

 (Russia) the *' brown Jura" predominates, it seems that the 

 German *' Jura" forms the transition from the " Jura" of the 

 north to that of the south, where the " white Jura'** has its 

 chief development. The English-French gulf of the Juras- 

 sic sea, in the middle of whiclv we now find the Paris and 

 London basin, constitutes, with its " oolite" formations, an 

 isolated group analogous to that of the northern " Jura," with 

 its masses of '* brown Jura." The fauna of the north exhi- 

 bits but slight differences ; but the contrary obtains with the 

 formations and inhabitants of the southern Jurassic sea, 

 stretching over Italy and Greece towards Africa and Asia. 

 In the middle, between north and south Europe, lies the 

 German "Jura," separated from that of the north-west by 

 the absence of the " great oolite," but generally containing 

 in itself the substances of the northern and the southern 

 " Jura," and at all events forming, by its coral bank, the north 

 edge of the northern Jurassic sea." — Leonhard U. Bronn's 

 Neues. Jahrbuch fiXr Miner alogie, U.S.W. 1850, 2 H. — The 

 Quarterly Journal of the Geological Society, vol. vii.^ No. xxvi., 

 p. 42. 



* Quenstedt. Petref. Deutsch., p. 264. 

 VOL. LI. NO. CI. — JULY 1851. 



