8 INVERTEBRATE PALAEONTOLOGY 



of the trend of evolution, generally and in detail, leads 

 automatically to improved precision in the interpretation 

 of the records of Stratigraphy. It is sufficient to refer 

 to the chaos of uncertainty that enshrouds the Pre- 

 Cambrian era, and to compare that ignorance with the 

 relatively clear understanding of such a period as the 

 Jurassic, to show that Historical Geology is practically 

 dependent upon fossil evidence. Of late years, detailed 

 study of the palaeontological characters of Graptolites, 

 Corals and Ammonites has revealed features of immense 

 theoretical and practical importance to Stratigraphers. 

 The long, and too often misleading, lists of fossils that 

 occur in most stratigraphical papers are testimonies to 

 the fundamental value of Palaeontology in such research. 

 Not only do fossils supply evidence for comparative 

 " dating " of rock-systems, but by the modifications and 

 proportions shown by faunal groups, they indicate the 

 conditions prevalent during their existence. Attempts 

 to restore the physiography of past periods gain more 

 reliable support from Palaeontology than from study of 

 the lithology of sediments or even description of the 

 known distribution of strata. It is not for a Palaeonto- 

 logist to write an apology for the study of Geology, but 

 he would be an unreasoning sceptic who doubted the 

 practical value of that Science. And Stratigraphy, the 

 culmination of Geological inquiry, depends almost 

 wholly upon the evidence that Palaeontology alone can 

 provide. 



Thirdly, the archaic school of Biology that was con- 

 tent to restrict its activities to the study of existing 

 organisms, regarding fossils as interesting, though some- 

 times inconvenient, " extras," is now well-nigh extinct. 

 A student of human history who strove to understand 

 and explain the intricacies of diplomacy that led up to 

 the recent world war without reference to any events 



