8 BIOLOGICAL SOCIETY OF WASHINGTON. 



ally related to each other by their respective faunas and floras 

 which certainly were not contemporaneously deposited, but also 

 that many foreign formations contain faunas which respectively 

 embrace homotaxial representatives of two or more European 

 formations. After I had selected the subject, and written out the 

 greater part of these remarks, the address of Mr. W. T. Blanford 

 and the article of Mr. J. Starkie Gardner, read before the British 

 Association for the Advancement of Science, at Montreal, reached 

 my hands. I find from a perusal of them that both of those 

 gentlemen have so far anticipated much which I intended to say 

 that I cordially recommend my hearers to read those productions. 

 Both of them, especially that of Mr. Blanford, record some start- 

 ling exceptions to the generally received rule that formations 

 homotaxially related were of contemporaneous origin. I shall 

 have occasion to refer to some of the cases of this character 

 which they have mentioned, and I shall also cite other instances 

 which have come under my own observation. First, I shall 

 mention instances where there is apparent reversion of the chro- 

 nological order of the formations, and afterward those in which ii 

 commingling in one formation of the characteristic types of two 

 or more epochs occur. 



Mr. Blanford, in his address, cites a considerable number of 

 instances where the order of occurrence of faunal and floral types, 

 according to the accepted chronological scale, is reversed. One 

 of these instances occurs at the famous Pikermi beds, near the 

 ancient city of Athens. These beds contain a rich mammalian 

 fauna which is so characteristically Miocene that the French 

 committee of the International Congress of Geologists specially 

 mention it as of that age. Some of the species of the Grecian 

 locality referred to are identical with those of some of the fully 

 recognized Miocene strata of other parts of Europe. Now, Pro- 

 fessor Gaudry found in the lowest of these Grecian beds which 

 bear Miocene vertebrates several species of well-known Pliocene 

 mollusca, and he also found that this bed in turn rests upon a 

 •• marine bed of undoubted Pliocene age." 



