376 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 29, 



The Avicula contorta beds and the Subdivisions of the Lower Lias 

 proposed in this Memoir, compared with the Classification of the 

 same strata adopted by other British geologists. 



Ammonite-zones 

 adopted in this 

 Memoir. 



Sir R. Murchison's 

 ' Geology of Cheltenham. 



SirH.Dela 



Beche's ' Section I 



at Lyme Regis,' I 



Geol. Trans. 2 ser. 



vol. ii. ! 



Rev. W. Cony- 

 beare's ' Geo- 

 logy of En- 

 gland and 

 Wales.' 



Zone of 



Ammonites 



raricostatus. 



Zone of 

 Ammonites 

 oxynotus. 



Zone of 



Ammonites 



obtusus. 



Zone of 



Ammonites 



Turneri. 



Zone of 

 Ammonites 

 Bucklandi. 



Zone of 

 Ammonites 

 planorbis. 



Hippopodiu.ru- N 



bed. 

 Cardinia-bed. 



> Ammonite-bed. 



Lower Lias 

 ► Shales (in 

 part). 



Upper Marl 

 (in part). 



Plagiostoma- ^ 

 beds. 



Zone of 

 Avicula con 

 torta (upper 

 part of the 

 Keuper). 



Saurian-beds. 

 Insect-lime- 

 stone. 



Bone-bed. 



Lower Lias 

 i Limestones 

 ' and Shales. 



Blue Lias. 

 Limestone. 



White Lias. 



Lower Marl. 



Red or Keuper Marls. 



Bed Marl. 



Upper 

 Marls. 



True Lias 

 Beds. 



Lower 

 Marls. 



New Bed 

 Sandstone. 



§ II. The Zone op Avicula contorta. 



Yon Buch, " Schicht mit Gervillien auf der Gruber Alp am Setz- 

 berge in den bayr. Alpen," Denkschr. Akad. Wissensch. Berlin, 

 Jabrg. 1828, p. 82. Alberti, " Versteinerungsreicber Sandstein von 

 Tabingen," 1834. Strickland, " Calcareous Sandstone witb Pectens, 

 and Wbite Micaceous Sandstone witb bivalve shells," Proceedings of 

 tbe Geological Society, 1842, vol. iii. p. 586. Portlock, " Sbale " witb 

 Avicula contorta, and " loose gritty marl " containing Pecten Valoni- 

 ensis, Beport on Geology of Londonderry (1843), pp. 126,127. Brodie, 

 " Pecten-bed," Fossil Insects of tbe Secondary Bocks (1845), p. 58. 

 Quenstedt, "Gelbe Sandsteine," Flozgebirge Wiirttembergs, 1846. 

 Emmerich, " G<?rvillien-Schichten," Neues Jahrbuch, 1849, p. 437. 



