207 



shells were obtained therefrom. The laminated clays of 

 Christian Malford were likewise extensively worked for fossils, 

 and from these various sources of knowledge we learn that the 

 Oxford Clay of Wilts may be thus divided into three zones, 

 taking the dominant Ammonite in each zone as characteristic 

 of it. The following table explains the sequence of the beds 

 in the Trowbridge railway cutting : — * 



LiTHOLOGT. Zones. Leading Fossils. 



Coralline Oolite. 



"Soft variegated siliceous 

 sands alternating with 

 calcareous giits and 

 bands of siliceous 

 sandstone containing 

 shelly fragments ; the 

 beds full of oblique 

 lamination, near Calne. 



Ammonites 

 Peeaematus. 



Ammonites perarmatus, 

 Amm. cordatus, Amm. 

 Lamberti, Amm. 

 Sutherlandise, Amm. 

 Crenatus. 



I 



ft? 



'Dark bituminous slaty- 

 clay containing sep- 

 taiia and veins of 

 stone with large Am- 

 monites ; the laminated 

 clays have the shells 

 of Ammonites and 

 other Molluscs well 

 preserved, but much 

 compressed as at 

 Christian Malford. 



Ammonites 

 Jason. 



Ammonites Jason, Amm. 

 lunula, Amm. Eegin- 

 aldi, Amm. Comptoni, 

 Belemnites Puzosi- 

 anus, B. abbreviatus, 

 Acanthoteuthis anti- 

 quus, Sepia, Loligo, 

 Alaria armigera, 

 Turritella muricata, 

 Trigonia clavellata, 

 Nucula Phillipsii, 

 Ostrea deltoidea. 



Pusty, yellow-coloured, 

 sandy Limestone, 

 passing into grey, Kel- 

 loway Mill and rail- 

 way cuttings. Wilts. 

 Scarboro', Yorkshire. 



Ammonites 

 Calloviensis. 



Amm. calloviensis. Am. 

 Gowerianus, Am. mo- 

 diolaris. Am. Konig^, 

 Ancyloceras callovi- 

 cense, Isocardiatenera. 





feel 



Dark, drab, or bluish 

 clay containing many 

 nodules, having Am- 

 monites for a nucleus, 

 railway cutting, near 

 Trowbridge. 



Ammonites 

 Maceocephaliis. 



Am. macrocephalus, 

 Amm. modiolaris, 

 Am. Gowerianus, 

 Am. Chamusseti, Am. 

 funiferus. 



Combrash. 



* A very good section of the Trowbridge cutting, carefully measured and 

 accurately described by Reginald Mantell, Esq., C.E., was published in the 

 Quarterly Journal of the Geological Society, Vol. ivi, p. 310 : 1850. The lists of 

 fossils and description of new species by Professor Mobbis, F.G.S. 



Q 



