ZONE OF A MALTHEUS IBEX. 



81 



Zone of Belemnites clavatus. 



Petrology. iHii-«. Fossils. 



NESS. 



Grey-bluish marls, tender, plastic, without 



Metres. 





interposed calcareous layers 



A thin layer of bluish "lumachelle," very hard, 



:> to 10 



Tisoa siphonalis, Marcel de Serres. 



charged with pyrites, forming very resist- 

 ing plaquettes. ... .. 



GO to 70 



Lingula Voltzii. 



Tisoa siphonalis, Marcel de Serres. 



Greyish-blue marls, without hard beds 



Marly limestones, alternating with yellowish 



marls and greyish ferruginous nodules 



Greyish marly limestone, coarse, hard, and 

 earthy, very often coloured blood-red 



2 to 3 

 2 to 3 



Belemnites paxillosus, Schloth. 

 Aegoccras armatum. Sow. 



( 



73 to 94 





Total thickness j in the 



(. two zones. 



Lower Lias. 



It was not possible in this region to correlate the beds by the Ammonites as he had 

 done in other Departments of the Rhone basin, so M. Dumortier selected Peden 

 (Bquivalis and Belemnites clavatus as the organic forms that characterise the different 

 horizons into which he has divided his zone of Belemnites clavatus. 



9. The Zone of Amaltheus Ibex. 



Synonyms. — " Upper Marls," pars, De la Beche, " Lias of Lyme Regis," ' Geol. Trans.,' 

 2nd series, vol. ii, p. 22, 1823. " Ochraccous Lias," Murchison, ' Geol. of Cheltenham,' 

 2 Ed., p. 42, 1845. "Die Schichten des Ammonites Ibex" Oppel, ' Die Juraformation,' 

 p. 122, 185G. " /^cd'-bed," Wright, 'Quart. Jour. Geol. Soc.,' vol. xiv, p. 25, 1858. 

 " Schicht. des Ammonites Centaurus,'" Emerson, ' Die Liasmulde v. Markoldendorf,' p. 34, 

 1870. "Die Schichten des Ammonites Centaurus," Brauns, 'Untere Jura,' p. HI, 1871. 



This zone was originally exposed at Battledown Hill, near Cheltenham, where it was 

 worked for brick-earth : the bed consisted of an unctuous, tenacious, yellowish clay, con- 

 taining numerous hard ferruginous nodules, many of which enclosed fossil shells. The 

 same stratum was found in Leckhampton, Charlton Kings, and Churchdown to the south, 

 and at Dumbleton, north of Cheltenham ; everywhere the nodules yielded many well- 

 preserved Mollusca, and the following list is characteristic of this zone. 



11 



