PRESIDENTIAL ADDRESS. 11 



other ; and those discrepancies amount to an actual reversion of 

 the usual order. In the cases which I shall now mention, how- 

 ever, the discrepancies consist in either the actual or relative 

 earlier introduction, or later continuation, of certain types among 

 both marine and continental faunas and land floras, than is 

 required by the European standards. In these latter cases there 

 is of course a confusion of homotaxial relationship, of the forma- 

 tions which contain the commingled types, with other forma- 

 tions ; but there is not necessarily any reversion of the order of 

 occurrence of the types, as there is in the cases already men- 

 tioned. 



I ou»ht not in this connection to omit mention of the so-called 

 colonies of Barrande. in Bohemia, which, as he contended, bear 

 ;i marine .Silurian fauna, alternating with strata which bear a 

 Primordial one. But as the truth of Barrande's position has 

 been seriously questioned, I need not discuss it in these remarks. 



Even after what we have seen of the history of the received 

 opinions concerning the synchronism of formations, it is still a 

 somewhat remarkable fact that, although the blending of the 

 faunas of certain formations into each other by the commingling 

 of types, which are regarded as characteristic of each respectively, 

 has been so long known and so often demonstrated, that the idea 

 of universal restriction of types to narrow time-horizons should 

 be so persistently held. Indeed, the fact that such a commin- 

 gling of types as I have referred to has been so well recognized 

 that it has made its impress upon the terminology of geology. 

 Thus the term Permo-Carboniferous has long been used in 

 America to designate strata which partake of both Coal-Measure 

 and Permian characteristics ; and the same term has been ap- 

 plied by Dr. Toula to strata which bear a similar fauna on the 

 island of Spitzbergen. 



The terms Cretaceo-Jurassic and Cretaceo-Tertiary have been 

 respectively applied to New Zealand strata for obvious reasons. 

 The former term has also been applied to Chilian strata by 

 Darwin ; and the latter, (but erroneously, I think,) to the Lara- 



