89 



are sought to be made with various isolated deposits widely 

 separated. 



Generally, liori/ontal extension of a particular species from 

 its orignal centre may represent a period of time during 

 which vast deposits may have accumulated, vertically, on the 

 original habitat, where each succeeding layer, perhaps, shewed 

 a gradual extinction of the older forms, and the introduction 

 of a new class of organisms. Thus, for example, could we 

 depress the present group of tertiary beds at Table Cape so 

 that the marine beds now in process of formation rested 

 conformably upon them ; a vertical section would show such 

 a complete change in the character of the various beds as to 

 justify the local geologist in sub-dividing his section into 

 separate groups with, locally speaking, well marked characters. 

 At the same time could we follow the horizontal movement of 

 organisms as they gradually disapjieared from the original 

 centre, we would yet find in a very far distant part of the 

 earth's surface, that amid all the vicissitudes of migratory 

 change, a few persistent forms of the lowest stratum of the 

 original centre would still be found to be the true contem- 

 poraries of those new forms which gave a complete change of 

 character to the upper beds. 



It follows from considerations of this nature that the exist- 

 ence of a few specific forms common to two or more widely 

 separated deposits, is, in itself, no guarantee that they belong 

 to the same subdivision of a great class ; or even to the great 

 class division itself. 



Such being the case we should accept with the greatest 

 caution the subdivisions of the various widely separated 

 tertiary marine deposits of Victoria into OUgocene, Miocene, 

 and Pliocene, until we know more fully the extent and c|uality 

 of the evidence which forms the basis of their classification. 



It also follows that until we have worked up independently 

 and fidly each deposit of the tertiary period, and also com- 

 pared them with a fully worked up list of existing forms in 

 the same neighbourhood, any attempt at classification will be 

 premature and misleading. 



Being deeply imi^ressed with the importance of such con- 

 siderations I have most carefully gone into the investigation of 

 our Table Cape marine deposit, and I have been rewarded 

 in the discovery of the remains of at least 150 distinct specific 

 organisms. When the great number of new species are 

 described and classified by the Eev. J. E. Tenison-Woods, to 

 whom science in Tasmania is already so deeply indebted, we 

 shall then be in a better position to compare with similar 

 deposits elsewhere and with the existing forms in our own 

 neighbourhood. But it is not enough to have our owu 



