MARCOU ON THE NEOCOMIAN AND THE WEALDEN ROCKS. 3 



D'Orb, ; Stijlina intricata, From. ; and Thamnastrcea dumosa, From. 

 Typical localities ; vicinity of Salins, Gray, Besangon, Montbeliard, and 

 Borrentruy. 



The Salins Limestone terminates the Jurassic strata, and a "well- 

 marked discordance of stratification exists between it and the Neoco- 

 mian rocksj a discordance varying from 5° to 15°, and which may be 

 seen on all the flanks of the different longitudinal valleys of the Jura. 



The Neocomian rocks are divided into three groups : the Lower 

 Neocomian, or Sfc. Croix gToup; the Middle Neocomian, or Chateau 

 gi'oup; and the Upper Neocomian, or Noirvaux group. 



The Lower Neocomian has its type in the vicinity of St. Croix, a 

 village in the Canton de Vaud, celebrated for the numerous and suc- 

 cessful researches of Dr. Campiche, who has collected there the most 

 complete set of Neocomian fossils in existence. Professor Pictet de- 

 scribes them in his Materiaux poiLr la Paleontologie Suisse, seconde serie ; 

 Description desfossiles du Terrain cretace de Ste. Croix, now in course of 

 publication. The St. Croix group may be divided into three princi- 

 pal parts, (a) the Villars Marls, {h) the Auberson Rocks, and (c) the 

 Metabief Limonite. 



(a). The Villars Marls (Marnes de Villars), forty feet thick, consist 

 of very hard, grey marls, alternating near the top with marly and 

 very compact limestone. In some places, such as Renaud du Mont, 

 La Riviere, and Foucine, the marls become green and even variegated, 

 and then contain layers of white gypsum and dolomitic limestone. 

 Professor Lory of Grenoble has found freshwater shells in this division, 

 such as Flanorbis Lor7/i, Coq.; Physa Wealdina, Coq.; Paludina, Cyclas, 

 Anodonta, &c. ; and M. Renevier has lately discovered the Gorhula 

 alata, Sow., which indicates a mixture of brackish- water animals. The 

 typical localities for fossils are, Yillars-le-lac near Morteau, Charix 

 near Nantua, Jongue, Les Rousses, and Cinquetral near St. Claude. 



(h). The Auberson Rocks {Roches d'' Auberson), eighty feet thick, are 

 composed of a series of compact, whitish, oolitic limestones, with beds 

 of blue and yellow marls, varying in thickness from half-a-foot to ten 

 or twelve feet, intercalated near the base. The marls contain in great 

 quantity a small sea-urchin called Toxaster Campichei, Pic, and a small 

 Terehratula related to the Ter. hiplicata, var. acuta, von Bucli. In the 

 limestone beds are found, Stromhus Sautieri, Coq.; Sigaretus Fidanceti, 



B 2 



