166 NATURAL SCIENCE [March- 



forms themselves may be, as in the Australian seas, very old and 

 primitive types, while in our seas they are very young and 

 specialised types. The Lingula, which has been extinct in 

 European seas since remote geological time, still lives in the 

 Australian seas. The conservation of the biological record is as 

 remarkable in some latitudes as its tendency to radical change is 

 in others, and we are utterly deluding the student with false notions 

 of contemporaneity of deposition, of homotaxis or other similar 

 homologies when we apply the same name to two widely separated 

 beds, not because they contain the same or a similar faima, but 

 because the proportion of living to extinct forms is the same, or 

 nearly the same, in each. We do not put negroes and Europeans 

 in the same category because in some cases there is the same pro- 

 portion of rogues to lionest men among them, or because of any 

 other purely adventitious circumstance. 



A truly scientific classification of the Tertiary beds must, if it 

 is to have any permanent value, be based on more stable data than 

 the proportionate numbers of living forms to extinct ones which 

 occur in a particular bed. The futile character of this criterion 

 applies to it under all circumstances and in all kinds of beds, 

 subaerial or otherwise. 



In the case of the Tertiary beds, however, the classification in 

 (question became more especially inconvenient and misleading since, 

 without any explanation or justification and in a measure surrep- 

 titiously, a mode of classifying beds dependent experimentally upon 

 the proportion of the mollusca in the marine beds was transferred to 

 a series of subaerial' beds, Avhere the same criterion was never in 

 fact used as a touchstone. This was done apparently on the very 

 superficial ground that De Beaumont had divided the extinct 

 mammals into three series, respectively marked by the palaeotheria, 

 the mastodons and elephants, and this threefold division of the 

 mammalian fauna of the Tertiary beds was adopted and incorporated 

 liy Lyell into his scheme for arranging the marine Ijeds without 

 any inquiry as to whether the divisions in the one case corresponded 

 with the divisions in the other, or could consistently be made to so 

 apply. Names originally based on facts derived from the molluscs 

 were quite arbitrarily applied to facts derived from land animals. 

 This is a very good instance of what T have complained of, namely, 

 the condensino- of submarine and subaerial beds into a common series 

 with common names. 



On these and other grounds I venture to distrust and rebel 

 against Deshayes' and Lyell's criterion for distinguishing the various 

 divisions of the Tertiary period and the conclusions based on 

 them. 



Let us now advance again and approach more concrete ground. 



