ZONE OF AMALTHEUS IBEX. 



81 



Zone of Belemnites clavatus. 



Petrology. Thick- Fossils. 





Grey-bluisli marls, tender, plastic, without 



Metres. 







.') to 10 



Tisoa siphonalis, Marcel de Serres. 



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





charged with pyrites, forming very resist- 







ing plaquettes 





Lingula Foltzii. 



Greyish-blue marls, without hard beds 



60 to 70 



Tisoa siphonalis. Marcel de Serres. 



Marly limestones, alternating with vellowish 







marls and greyish ferruginous nodules 



2 to 3 



Belemnites paxillosus, Schloth. 



Greyish marly limestone, coarse, hard, and 







earthy, very often coloured blood-red 



2 to 3 



Aegoceras armatum, Sow. 



( 



73 to 94 





Total thickness :.... { 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. Duraortier selected Feclen 

 (squivalis and Belemnites davaftis 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. " Ochraceous Lias," Murchison, ' Geol. of Cheltenham/ 

 2 Ed., p. 42, 184.5. "Die Schichten des Ammonites Ibex" Oppel, ' Die Jm-aformation,' 

 p. 122, 1856. "/5ea'-bed," Wright, 'Quart. Jour. Geol. Soc.,' vol. xiv, p. 25, 1858. 

 " Schicht. des Ammonites Centaiirus" Emerson, ' Die Liasmulde v. Markoldeudorf,' p. 34, 

 1870. "Die Schichten des A7nmonifes C'entaurus," Brauns, 'Untere Jura,' p. Ill, 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 



