540 Geological Society. 



of the species, and to correlate systematic relationships with geogra- 

 phical distribution. He believes that this evolution has proceeded 

 by " a combination of orthogenetic aud adaptive modifications 

 which have led to various parallel series in this family." 



The publication of this volume coincides with Dr. Boulenger's 

 retirement from the service of the Natural History Museum, and 

 all zoologists must regret that the most distinguished of living 

 herpetologists is no longer officially connected with the unrivalled 

 collection which he has done bo much to build up. 



PROCEEDINGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



May 5th, 1920.— Mr. G. W. Lamplugh, F.R.S., 

 Vice-President, in the Chair. 



The following communication was read : — 



'A Natural "Eolith" Factory beneath the Thanet Sand.' By 

 Samuel Hazzledine Warren, F.G\S. 



The paper describes a section in the Bullhead Bed at Grays, 

 where the conditions have been favourable for the chipping of the 

 Hints by subsoil pressure. There is evidence of extensive solution 

 of the Chalk beneath the Tertiary deposits, and the differential 

 movements thus brought about have occasioned much slickensiding, 

 and remarkable effects in the chipping of the flints. 



In the Author's opinion the section affords the most complete 

 and conclusive evidence hitherto obtained in support of the theory 

 of the origin of the supposed Eolithic implements hy purely natural 

 agencies. There are not only the simpler Kentish types, such as 

 notches, bowscrapers, and the like, but also the larger and more 

 advanced forms of rostro-carinates which are characteristic of the 

 sub-Crag detritus-bed. Careful digging enables the pressure-points 

 of one stone against another and the resultant chipping effects to 

 be studied in detail; and in many instances the flakes removed can 

 be recovered and replaced. 



A few examples are more than merely Eolithic in character. If 

 such exceptional examples were removed from their associates, and 

 also from the evidences of the geological forces to which they have 

 been exposed, no investigator could be blamed for accepting them 

 without question as of Mousterian workmanship. Individual 

 specimens may often deceive : in order to distinguish a geological 

 deposit of chipped flints from the debris of a prehistoric chipping- 

 lloor, it is necessary to base one's judgment upon fairly representa- 

 tive groups, and also to take into consideration the circumstances 

 in which they have been discovered. 



