1883-1884.] ^ 



England, are characteristic of the Cretaceous period. This con- 

 flicting evidence has uniformly been decided in favour of the 

 better known mollusca, and that of the little known plants has 

 been justly set aside. In all the cases into which I have 

 examined, the supposed purely Cretaceous fauna contains a large 

 number of types which are quite unknown in our true Cre- 

 taceous rocks, and which seem to me to denote a marked 

 approach to those of the Tertiary. These faunas require very 

 cautious and critical examination, for even the humblest groups 

 of mollusca have steadily progressed from primaeval to modern 

 forms, and the recognition of the precise stages they had reached 

 on the journey, when summed up, should afford a tolerably safe 

 indication of the relative age of the rocks in which they occur. 

 It is unworthy of science to suppose that all the types char- 

 acteristic of the Cretaceous were extinguished at once, for a 

 great many still exist, and the presence of a Belemnite, Baculite, 

 Ammonite, or Inoceramus, should no more be received as con- 

 clusive evidence of the synchronism of a bed with our Chalk, 

 than the presence of a Nautilus, Cidaris, Salenia, Terebratula, 

 Trigonia, Pleurotomaria, or any other of the scores of Cretaceous 

 genera that are still existant. Numerous plants have been obtained 

 from our Neocomian, Gault, and even grey Chalk, without any 

 trace of the presence of dicotyledons, yet beds abounding in 

 dicotyledons of still existing genera are correlated with them on 

 the strength of the Cretaceous aspect of a percentage of their 

 mollusca. I can only say that if these floras are truly contem- 

 poraneous with our Chalk, there is nothing to prevent our 

 assigning a Cretaceous age to the floras of Mull and of Antrim. 



Besides the Cretaceo-Eocene period, to which at least the 

 earlier outpours might be assignable, we have the entire Eocene 

 formation, a fragmentary record in England of only some 2000 

 feet thick, but attaining in the nummulitic formations of the 

 East to prodigious thicknesses. The actual, direct, palseonto- 

 logical evidence, connecting the plants of the Basaltic formation 

 with those of the Eocene period, I must postpone until a future 

 time. I can only now say that if asked to pick out the flora 



