part 4] JURASSIC chronology. 453 



Table VI — Sketch of the Chronological Sequence in the Upper Lias. 



Ages 



. Bed Nos. 





Hemerae. 





Strata. 





" 



9. 



moorei. 



"j 









8. 



CatuUoceras. 



( 



> Yeovil Sands. 



^ 





7. 



Dnmortieria. 



J 





M 





6. 



Hammafoceras. 





Bruton Sands. 



•§H 





r 5. 



dispansum. 





Frocester Beds. 



> 



o 





4. 



strucTcmanni. 





Midford Sands. 



P4 



U.L. 28. 



3. 



pedicum. 



> Stinclicombe Beds. 







2. 



eseri. 











. 1^ 



striatulum. 





Sodbury Sands. 





^ U.L. 27 c. 



26. 



variabilis. 



■> 









25. 



lillL 



I 



' Cotteswold Sands. 





U.L. 27 5. 



24. 



semipoUtum} 



J 



1 





U.L. 27a. 



23. 



S'lobplanatum. 



> 



) 







22. 



braunianum. 





> Nortbampton Beds. 







21. 



fibulatum. 



J 







U.L. 26. 



20. 



bifrons. 





1 





U.L. 25 ? 



19. 



18. 



subcarinata. 

 pseudovatum. . 



-> 



^ Wbitby Beds. 





U.L. 24. 



17. 



Gen. and sp. nov. 



■^ 











(small Harpocerate.) 







U.L. 23. 



16. 



Hildocei'afoides. 







■M 



« J 



U.L. 19. 

 U.L. 18. 



15. 

 14. 



falciferum. 

 midaites. 





' Bavrington Beds. 





U.L. 15. 



13. 



Cf. Pseudolioceras. 







U.L. IL 



12. 



atiguinum. 









U.L. 7. 



11. 



Sarpoceratoides. 











10. 



murlei/i. 





Dumbleton Insect-Bed. 







9. 



exaratum. 





Boulby Bed. 







r 8. 



bitbrm Havpocerates. 





Grantham Bed. 





U.L. 3. 



I 



Eleganticeras. 





■ Yorksliire Jet-Rock. 







^ 6. 



JElegantuliceras. 









5. 



tetiuicostatum. 





Yorkshire Grey Shales. 





U.L. 2. 



4. 

 3. 



Tiltoniceras. 

 atlileticum. 



\ Tilton Beds. 





L U.L. 1. 



2. 



fine-ribbed Dactyloids. 





Stocklinch Bed. 



« 





1. 



Harpoceratoid. 





Chideock Bed. 



§5) 



[ M.L. 1. \ 



2. 

 1. 



Jiawskerense, 





Hawsker Beds. 



spiuatum. 





South Petherton Beds. 



Jet- Rock ; if placed afterwards, the former is avoided at the 

 expense of a double non-sequence in the Jet-Rock. Further 

 evidence is required. 



As the evidence for the chronology of the earlier hemerae of the 

 TJpper Lias is somewhat imperfect, the correlation-table (YII, 

 facing p. 454) has been drawn up, chiefly in order to compare 

 Somerset with Yorkshire. The lacunae in the intervening areas 

 are not all to be read as non-sequences : the}^ arise from lack of 

 evidence, collection-failure, exposure-failure, nomenclature-failure, 

 and so on. It is doubtful Avhether anything like the full sequence 

 of the early hemerse of the Whitbian has yet been obtained, 



1 midoeeras semipolitum, S. Backman, is the particular species of the lower 

 part of the Cotteswold Sands; evidence for itVZ/a lilli and its associates in that 

 deposit is lacking, but there is plenty of room for them. Very little collecting has 

 been done in this deposit, which sometimes is 250 feet thick. 



