280 



A. J. JUKES- BROWNE ON THE RELATIONS OF 



formation, in number 63, there are 147 left, out of which 109 are 

 common to the Gault (this gives 74 per cent.), and of these, 80 (or 

 54 per cent.) are characteristic of the upper stage ; the percentage 

 of Vraconnien forms is a little less than before, viz. 92, or more than 

 62 per cent. The above numbers show how much the fauna re- 

 sembles that of the Upper Gault ; but the close relation which exists 

 between them is still more prominently brought out when the most 

 common fossils are alone considered. It is these which always 

 indicate the true affinities of a fauna, whereas a catalogue of the 

 whole assemblage often prevents a proper estimation of its true 

 character. 



The present being just such a case, I have prepared the following 

 list of common fossils, most of which may be picked up on any heap 

 near Cambridge; of these, all except four may be found in the 

 Upper Gault of England, and these are supplied by the Gault supe- 

 rieur of the Continent. 



List of common Cambridge Fossils. 



Names. 



Lower 

 Gault. 



Upper 



Gault. 



Vraconnien. 



Upper 

 Green- 

 sand. 



Ichthyosaurus campylodon, Carter 



* 



# 

 X 

 X 



x 

 x 

 x 

 * 



X 

 * 



x 

 x 

 x 

 x 



X 



X 

 X 

 X 

 X 

 X 

 X 

 X 

 X 

 X 



X 

 X 



X 



* ********* ************* * 



x 



x 



x 

 * 



x 



x 



x 

 x 



x 

 x 





Belemnites ultimus, IX Orb. (var.).. 



Nautilus clementinus, IX Orb 



albensis, IX Orb 













Raulinianus, IX Orb 



Pleurotomaria Gibbsii, Sow 



Rhodani, Brogn 



Eouxi, D'Orb 



Deutalium decussatum, Sow 





Exogyra Rauliniana, IX Orb 









Terebratula biplicata, Sow 



Rhynchonella sulcata, ParJc 



Palseocorystes Stokesii, Mant 



Trochocyathus conulus, Edw 



• angulatus, Duncan 



Serpula articulata, Sow 





Total 30 



14 



26 



24 



11 



