MOOEE — ABXOEMAL SECOXD-^JRT DEPOSITS. 



461 



tion, is only typical at that place and at Hatch. This bed is there 

 about a foot in thickness ; and in no other locality have its fossils been 

 so perfectly preserved ; it is frequently very thin or entirely absent. 

 As we pass upwards into the " White Lias " group, we reach a 

 series of dense close-grained Hmestones, often Hght-blue at their 

 base and cream- coloured in their higher members. Although a few 

 of the testacea are common to the lower beds, and a few from the 

 " White Lias " pass agaiu into the true Lower Lias, still the palseonto- 

 logical change which occurs with these deposits is most remarkable. 

 In the Avicula-contorta zone and the Bone-bed just below are the re- 

 mains of jMammalia, land and marine Eeptiha, and Fishes of many 

 genera and species ; but, although I have examined almost every 

 known quarry of " ^Tiite Lias " between Bath and Lyme, I have 

 never obtained the slightest evidence of the presence of any verte- 

 brate remains, or of any Cephalopoda throughout them. Often 

 through considerable districts the " White Lias " will be found al- 

 most unfossiliferous, whilst in other localities the testacea will as 

 individuals be very numerous, although few in genera. Some phy- 

 sical change iu the character of the ocean must have occurred when 

 these beds were being deposited, in order to account for the entire 

 absence or extinction of the vertebrata, which must have teemed in 

 the previous seas, throughout so wide an area. Since we had in the 

 Avicula-contorta beds below a change from the fresh- or brackish- 

 water deposits of the Keuper, we have probably a recurrence to the 

 former conditions with the " White Lias," and therefore the destruc- 

 tion of all the marine vertebrata. The barrier thus interposed has, 

 I believe, not allowed a single species of Ehaetic vertebrata to 

 pass into the Lower Lias; for hitherto, although some genera pass on, 

 I have never, of this family, found any species common to both. 



in. 

 6 

 6 

 6 



a. Succession of Keuper, Wicetic, and Liassic Beds at Camel Hill Rail- 

 way-cutting, in ascending order. 



Keuper. ft. 



1. Grrey Marls 14 



2. Ditto with Strontian ...... 6 



3. Bed of Strontian 



4. Grey marls with well-de- 



fined layers of Sulphate 

 of Strontian 32 



5. Thinly laminated grey 



marl 1 



6. Grrey marl passing into 



blue 23 



7. Grey marl "^ 



2 6 



Bhsfic. 



Grey sandstone with Acro- 



c?M.s-teeth, Lepidotns- 



scales, &c., and casts of 



Axinus and otlier shells 



Carried forward 



80 



1 6 



24 



ft. 



Brought forward 82 



9. Grey marl 



10. Bluish sandstone 1 



11. Marl 



12. Soft yellow sandstone ... 2 



13. Blue shales, with Cardhim 

 Bh(sticum,Avicida con- 

 torta, Axinus, &c. &c. 



14. Stone, Fecteoi Valoniensis 



15. Blue clay with ditto 



16. Stone with ditto 



17. Clay 



18. Stone, Avicula contorta, &c. 



19. Clay 



20. Stone 



21. Clay 



22. Stone, Fecten Valoniensis, 



&c 



m. 

 

 8 

 

 5 

 



6 

 3 

 2 

 3 

 2 



1 

 1 



2i 



Carried forward 112 Oi 



