328 On the Comhrash of the neighbourhood of Cirencester. 



List of Fossils common to the Inferior Oolite and Combrash of 



Gluncestershire. 



1. Amphidesma securiforme, Phill. 12. Modiola gibbosa, M. C. 



York. (Gresslya.) 13. plicata, M. C. 



2. decurtatiim. Phill. York. 14. Mya literata, M. C. 



3. recurvum, Phill. York. 15. Ostrea, undetermined (perhaps 



4. Astarte excavata. several speeies). 



5. Avicula inajquivalvis, M. C. 16. Pholadoniya Murehisonse, M.C. 



6. Cardium citronoideum, Phill. t. 545. 



York. 17. gibbosa. 



7. dissimile, M. C. 18. Plagiostoma duphcatum. 



8. , undetermined. 19. Pecten. 



9. Isocardia concentrica. (Cero»i!/«.) 20. Trigonia costata. 



10. minima. 21. clavellata. 



11. Lima gibbosa, M. C. 491. 



Here then we have evidence of an older fauna reappearing in 

 force in a newer bed, and that bed of a very insignificant thick- 

 ness ; these facts, while they should make us cautious in assign- 

 ing limits to the range of fossils, may at the same time account 

 for much of the confusion felt in the history of the Oolites of 

 Britain, which only becomes the greater on comparison with the 

 " Jurassique " of the continent. 



These remarks are the more pertinent, when it is understood 

 that in Phillips's ' Illustrations of the Geology of Yorkshire,' 

 nearly all, if not every individual species figured as characteristic 

 of the Cornbrash are amongst the more common examples of 

 Inferior Oolite fossils. 



Now these species, except in a few instances, are not common 

 alike to the Great Oolite of this district, but a reference to 

 Morris and Lycett's ' Monograph of the Mollusca of the Great 

 Oolite, chiefly from Minchinhampton and the coast of Yorkshire,' 

 will tend to explain how the parallelism of the Inferior Oolite 

 and Cornbrash species of this district could be maintained by the 

 Great Oolite of the more northerly oolitic deposits. In the 

 introduction to the memoir cited, p. 6, are the following re- 

 marks: — "The evidence afforded by the few species of univalves 

 which have been forwarded to the authors from Scarborough, 

 through the kindness of Mr. Bean, though not conclusive, tends 

 rather to assimilate them with the Inferior Oolite, and the 

 authors are led to the following very satisfactory explanation. 

 Admitting therefoi'e the parallelism of the deposits containing 

 somewhat distinct faunas in the north-eastern and south-western 

 parts of the present area of England, we are naturally led to 

 infer, either that the physical conditions might be favourable to 

 the continuation of species in one locality, or that species cha- 

 racteristic of an older deposit, in a more distant region, may 

 have migrated and lived on during the formation of a newer de- 



