﻿Vol. 6 1.] ANNIVERSARY ADDRESS OF THE PRESIDENT. Ixxvii 



apart should be made, in order to ascertain the changes which 

 take place laterally as well as those which occur in the vertical 

 succession. The task would not be easy, owing to the frequent 

 appearance of a particular form in exceptional abundance on one 

 bedding-plane ; and for this reason, notwithstanding very detailed 

 work, some differences would be due to the non-detection of certain 

 of the fossils. But, notwithstanding this, it is clear that such 

 numerical estimates would go far towards adding to our knowledge 

 of the changes which take place in the faunas, and many now 

 obscure points might be cleared up ; in particular, we should 

 discover whether at certain horizons a marked change in the faunas 

 takes place with exceptional suddenness, without any obvious change 

 in the character of the sediments to account for it. 



In carrying out such a piece of work, all the lithological changes 

 should of course be noted, and also the existence at some horizons 

 of changes in lithological character without the presence of a 

 bedding-plane (in the form of a plane of discontinuity marking 

 temporary cessation of sedimentation), and at others of such planes 

 of discontinuity severing in some places rocks of similar, and at 

 others rocks of dissimilar, lithological characters. 



Work of this nature will go far to correct many inferences which 

 havo been drawn as the result of casual collecting. It is surprising 

 how many fossil lists of the organisms contained in the strata of our 

 own island have been drawn up as the result of a few hours', or at 

 most of a few days', work by the collector. Little wonder that the 

 faunas of contemporaneous beds at considerable distances should 

 often be judged to be very dissimilar. The Shineton fauna 

 described by Dr. Callaway as occurring in Shropshire was rightly 

 referred by him to the age of the Tremadoc Slates, although the 

 fauna was very different from that of those slates at Tremadoc 

 as then known. Eecent research has proved that this particular 

 zone of Tremadoc rocks had not then been discovered in the Tremadoc 

 district, and its subsequent detection has shown the similarity of 

 the fossils of that band in the Tremadoc and Shineton neigh- 

 bourhoods. Consider the rich fauna of the Wenlock Limestone 

 made known to us in a large degree by the work of Col. Fletcher, 

 Dr. Grindrod, and others, carried on through many years. What 

 should we have known of this fauna, if a collector had merely 

 hammered at the rocks for a few days, as has been done in the case 

 of so many other deposits ? 



The rough-and-ready methods which, in some cases, have been 

 pursued in compiling lists of fossils of the different sediments would 



