A. J. Jukes- Browne — On the term Neocomian. 313 



Lastly, in 1854, Prof. Eenevier, of Lausanne, described certain 

 beds, which had previously been called Lower Aptien, as a separate 

 subdivision under the name of Ehodanien, and in 1856 he published 

 a brief note " On some points in the Geology of England," in which 

 he announced the results of a visit he had made to England for the 

 purpose of comparing the Swiss and English beds. The results are 

 that the Lower Greensand is not the equivalent of the Neocomian, 

 but corresponds exactly with the Aptien, and that the fauna of the 

 Atherfield beds of the Isle of Wight has the strongest analogy with 

 that of these Lower Aptien or Ehodanien beds. Marcou, writing in 

 1858, says that he willingly adopts these conclusions and opinions of 

 M. Eenevier. 1 



Meanwhile, a further modification had been proposed by MM. 

 Coquand and Leymerie, who found a difficulty in separating the 

 Urgonien and Aptien groups in the Pyrenean district, where accord- 

 ing to their account the rocks contain a mixture of the fossils which 

 elsewhere occur in the Urgonien and Aptien ; they therefore proposed 

 to combine these two groups, calling the division thus formed the 

 TJrgo-Aptien, and admitting a Neocomian division below. This 

 suggestion has been adopted by Prof. Eenevier, who published the 

 following arrangement in 1874 (Tableau des Terrains Sedimentaires) : 



! Aptien 

 Rhodanien 

 Urgonien. 



, T . ( Hauterivien 



Neocomien | yalanginien. 



The facts upon which this scheme is founded require confirmation, 

 and the nomenclature proposed does not seem to have found much 

 favour, D'Orbigny's names being still generally employed by French 

 geologists. 



Having now explained the origin of this nomenclature, I proceed 

 to give the succession of the strata in question at some of the typical 

 localities. 



The most complete sections are to be found in the S.E. of France 

 (Departments of Vaucluse, Drome and Isere), where the succession 

 is as follows, according to MM. Cornuel and Lory. 



/ Greenish sandstones. 

 Marls with Belemnites semicanalicutus, Ammonites nisus, Martini and 



Jissicostatus. 

 Marls with Orbitolites and other fossils. 



Aptien. 



i Limestone with Caprotina (Requienia) Lonsdalei. 

 Marls with Orbitolites and Heteraster oblongus. 

 Limestone with Cajirotina (Requienia) ammonia. 



fMarls with Toxaster complanatus. 



Marly limestones with Ancyloceras Duvalii. 



Glauconitic limestones with Bel. dilatatus. 



Red limestone with Ostrea Gouloni and Bygurus rostralas. 



Limestone of Fontanil. 



Marls with Bel. latus and Am. neocomien sis. 



Argillaceous limestones with Am. astierianus. 

 ^Limestones with Terebratula diphyoides. 



1 Sur le Neocomien dans le Jura, Zurich, 1858, p. 63. 



Neocomien. 



