part 4] JURASSIC CHiioxoLour : lias. 327 



Mr. G. W. LAMPLuaH said that, while recognizing the scientific 

 value of this intensive study of the Liassic ammonites, he feared 

 that the Author's continued refinements of the nomenclature and 

 zonal classification had carried the subject beyond the reach of the 

 ordinary field-geologist. From the imperfect nature of the evi- 

 dence, such exactitudes as those shown in the tables could rarely 

 be applicable in the field. The use of fossils by the stratigrapher 

 in the past, though crude, had generally been effectiv^e for his 

 purpose ; but he could not be expected to master the complicated 

 technicalities of these new methods. The stratigraphical deduc- 

 tions drawn solely from these pala^ontological studies did not 

 inspire confidence. 



Dr. J. W. EvAXS thought that the questions raised by the paper 

 were of considerable importance, with reference to the problem of 

 determining the time occupied in the deposition of sediments. If 

 the numerous non-sequences believed by the Author to exist were 

 substantiated, there could be little doubt that there must be many 

 more of shorter duration for which no pala^ontological evidence 

 was aA^ailable, and the conclusion would be justified that the 

 geological record was of a far more fragmentary character than 

 generally believed, and represented onlj^ a small fraction of the 

 time that actually elapsed. In this way would be explained the 

 contrast between the hundreds of millions of years for the age of 

 the Palaeozoic formations postulated by workers in the field of 

 radioactivity, and the tens of millions arrived at by those wdio 

 based their conclusions on the rate of deposition (see Proc. Greol. 

 Assoc, vol. xxiv, 1913, pp. 243-44). 



