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



The basement beds are only found at and south of Chambery, 

 while north of that place the Calcaire de Fontanil is the lowest bed, 

 resting on Coral Rag. M. Lory remarks that all the limestones 

 thicken northward toward Savoy and the Jura, while the marls in- 

 crease to the southward, and Prof. Hebert l states that the argillaceous 

 hydraulic limestones with Ammonites Astierianus attain a thickness 

 of 500 metres (1600 feet) near Chambery, the aggregate of the rest 

 of the Neocomian above these limestones having an equal thickness, 

 so that the total depth of this division here is at least 3300 feet. 

 There is some doubt whether the lithographic limestones with Ter. 

 diphya (janitor), which underlie those with T. diphyoides, should 

 not also be classed as Neocomian. Eenevier refers them to the 

 Portlandian, but Hebert places them in the Neocomian (thickness 

 350 feet). Near Grenoble the Urgonien is said to be 900 metres 

 (nearly 3000 feet) thick, but nowhere else does it reach more than 

 1300 feet. The Aptien is about 60 feet thick at Grenoble, but at 

 Bedoule it is as much as 650 feet, and in the Gard about 300 feet. 2 

 At Perte du Rhone, farther north, the section is given as follows by 

 Prof. Renevier : — 



Greensand with Ammonites mammillaris. 



iHard greenish sandstone, with Plicatula placunea and Am. 

 Cornuelianus. 

 bands without fossils. 

 Greenish sandstone with Oslrea aquila. 

 f Marly sandstones including a thin layer full of Orbitolites lenti- 

 | culata (33 feet). 

 I Clays without fossils (10 feet). 

 Ehodanien, 56 feet. <( Marls with Heteraster oblongus, Trigonice and Aporrhais Robi- 

 | naldina, etc. 



I Ked Limestone with Heteraster oblongus, Pterocera pelagi, and 

 (^ Caprotina Lonsdalei. 



(White friable limestones and grey compact limestones in 

 alternating beds, and containing Caprotina {Requienia) 

 ammonia : base not seen. 



By Pictet and Campiche the beds are differently grouped ; they 

 place the red limestone in the Urgonien, and class the overlying 

 marls and clays as Lower Aptien, the Upper Aptien here being very 

 thin. Sandy limestones with fossils of true Neocomian species occur 

 at a lower horizon, the above section only extending as far as the 

 confluence of the Rhone and Valserine. 



In the Jura and near Neuchatel the succession is given as follows, 

 the thicknesses of the lower beds being those given by Marcou : — 



Aptien and ( Greensands of Presta with Plicatula placunea. 

 Ehodanien. \ Yellow marl with Heteraster oblongus and Orbitolites. 



Urgonien, ( White limestone with Requienia ammonia. 

 150 feet. \ Yellow limestone with Goniopygus peltatus. 



! Yellow stone of Neuchatel. 

 Marls of Hauterive with Am. radiatus. 

 Limonite de Metabief with Pggurus rostratus. 

 Limestone of Auberson with Toxaster Campichei. 



1 Bull. Soc. Geol. de France, ser. 2, vol. 28, p. 142. 



2 for this and other information I am indebted to Dr. Ch. Barrois. 



