OF THE SWISS JTJEA AND ENGLAND. 



247 



marl, varying in thickness ; the fossils from these beds come prin- 

 cipally from the marls. 



In the neighbourhood of Brenets and Tillers -le-Lae there are 

 several sections in the rocks of this stage. Xear Brenets it is seen 

 as a thin-bedded, grey limestone, interbedded with fossiliferous marly 

 beds. Then, again, both sides of the Lac-des-Brenets are formed of 

 these Portlandian limestones, and in this locality present a striking 

 resemblance to the ^fountain Limestone in some of the Yorkshire 

 dales. Similar limestones are also seen below the Purbeckian 

 beyond Locle, and the whole series is well exposed in the gorge 

 leading from Keuchatel towards Yalangin, where the following 

 section was observed : — 



6. Thick series of thin-bedded, compact, grey limestones. 



5. Thick, compact, grey hmestones. 



4. Thin marly bed. 



3. Gray and compact hmestones. 



2. Marly bed. 



1. Thick series of dark-grey limestones. 



The Purbeckian of the Jura has attracted considerable attention, 

 and has been fully described by Jaccard and De Loriol, and again 

 by Halliard. Jaccard (op. cit. p. 176) makes out three subdivisions 

 in this stage : — 



An upper grey, oolitic and fissile marl, about | metre (20 inches) 

 thick, containing brackish-water fossils. This bed occurs at Yillers- 

 le-Lac, and also on the road to Yalangin, near Xeuchatel. In the 

 last-named locality it is represented by a marly bed, which contains 

 numerous scales of fish. This forms a passage into the overlying 

 Yalangian, and below it come some more thin-bedded marls and 

 limestones, with freshwater fossils. At Yillers-le-Lac these beds 

 contain numerous C/wra-spores. 



The middle Purbeckian is much more variable than the preceding. 

 Below the freshwater marls and limestones there is a fairly constant 

 bed of very porous and almost scoriaceous limestone, which passes 

 down into clayey beds containing numerous small bipyramidal 

 quartz-crystals, and carbonaceous material is sometimes present, as 

 are also crystals of gypsum. 



The lower Purbeckian consists principally of limestones, and in it 

 the following zones have been made out : — 



3. Limestone of scoriaceous texture (Dolomie celhdeuse), 13 to 16 feet. 



2. White, and sometimes oolitic, limestone (Dolomie saccharo'ide), with C'ar- 



dium villerense and Corbida infiexa, 6 feet 6 inches. 

 1. Fissile, thinly laminated limestones, 34 feet. 



Rone of the sections observed by us in this district showed these 

 three substages, and in most cases only a small exposure was visible. 

 At St. Imier greyish marly limestones with Limncm and Planorbis 

 were seen belonging to this stage. The section at Yillers-le-Lac, 

 which is perhaps the most typical for the Purbeckian in the Jura, was, 

 at the time of our visit, almost completely hidden by debris ; we 

 saw some thin grey limestones and marls with fossils, and below 

 these came clays with gypsum, and there were numerous small crystals 



