THE CAMBRIDGE GAULT AND GREENSAND. 



281 



The following Table is drawn up to show the absolute number 

 of species common to the two Cambridge faunas, and the others 

 to which they bear any relation. 



Table showing the Number of Species common to the Cambridge 

 Faunas and those of other Formations. 



Name of Fauna. 



Number 

 of 



Common 

 Species. 



Number 

 of 



Name of Fauna. 





Species. 



Species. 





Cambridge Coprolites 



210 



92 



240 



Gault superieur, or 



(Gault fauna). 









Vraconnien. 



>> , " 



210 



80 



110 



Upper Gault of Folke- 



' * 









stone and Bucks. 



j* » 



210 



64 



187 



Lower Gault of Folke- 

 stone and Bucks. 



it t-i 



210 



20 



72 



Upper Greensand (ex- 

 cept that of War- 

 minster). 



»> ti 



210 



28 



140 



Warminster Green- 

 sand. 



»> >> 



210 



21 



60 



Chalk-marl and Grey 

 Chalk — Cambridge, 

 &c. 



Cambridge Greensand 



44 



10 



110 



Upper Gault (Eng- 

 land). 



(indigenous fauna). 









j» >> 



44 



8 



240 



Gault superieur. 



j> jj 



44 



12 



•72 



Upper Greensand. 



ii h 



44 



14 



140 



Warminster beds. 



Si m 



44 



29 



60 



Chalk-marl and Grey 

 Chalk. 



Note. — These numbers do not include the species of Vertebrata. 



This comparison of the faunas will also enable us to take another 

 view of the two assemblages of fossils in the Cambridge Greensand, 

 and to ascertain which of the other formations contains the greater 

 percentage of Cambridge fossils. 



Considering the derived fauna first, its closest relations are evi- 

 dently with that of the English Upper Gault; 110 species are 

 known in that formation, and 80 of them (or 73 per cent.) occur at 

 Cambridge. 



Only 39 per cent, of the Vraconnien fauna are found in the Cam- 

 bridge bed ; but the lowness of this percentage is greatly due to the 

 mixed character of the Vraconnien fauna at Cheville, which contains 

 many fossils belonging to higher horizons than that of the true 

 Gault superieur, as well as many foreign species unknown in 

 England. The absolute number (92) is large. 



With the Lower Gault its relationship is much more remote : 

 187 species have been found in this division by Mr. Price, and 64 

 of these (or little more than 34 per cent.) occur in the Cambridge 

 Greensand; but it must not be forgotten that most of them are 

 among the rarest fossils of that formation. 



