1S70.] '*^ • [VViiicliolJ. 



enter upon an examination of the paleontological affinities of the Che- 

 mvmg group, with whicli it has been thought this Carboniferous assem- 

 blage of strata can be synchronized. I shall content myself, however, with 

 three remarks. 1. The fauna of the Chemung group embraces numerous 

 generic forms, some for the first time introduced, which were des- 

 tined to iindergo their full expansion and find their closest analogues in the 

 Carboniferous Age. 2. It embraces some generic and many specific forms 

 which lingered froni early Devonian times, and which do not pass the up- 

 per limits of this group. 3. The balance of affinities is universally ad- 

 mitted to be with the Devonian system, so that the attempt to establish 

 that proposition would be superfluotis. 



VII. Can the Marshall, and Chemung be Synchronized? 



Ever since Cuvier first enunciated the doctrine of successive faunas in 

 the past history of the world, geologists have held that paleontological 

 characters stand next in importance and reliability to observed superpo- 

 sition in the determination of the synchronism or sequence of formations. 

 Pictet'^2 lays down the following principles for our guidance in the use of 

 fossils : 



"1. In all coi\ntries which have been studied, to the present time, the 

 geological faunas succeed each other in the stime order." 



"2. Contemporaneous formations, or those formed at the same epoch, 

 contain identical fossils. ' ' 



"3. Reciprocally, formations which contain identical fossils are contem- 

 poraneous." 



Professor Agassiz, '^^ in writing of the " succession of animals and plants 

 in geological time," says: "I cannot refrain from expressing my wonder 

 at the puerility of the discussions in which some geologists allow them- 

 selves still to indulge, in the face of such a vast amount of well-digested 

 facts as our science now possesses. They have hardly yet learned to see 

 that there exists a definite order in the succession of these innumerable 

 extinct beings, &c. ' ' 



"One result stands now unquestioned; the existence during each geolo- 

 gical era of an assemblage of animals and plants differing essentially for 

 each period. And by period I mean those minor sub-divisions in the suc- 

 cessive sets or beds of rocks whicli constitute the stratified crust of our 

 globe, the number of which is daily increasing as oui" investigations be- 

 come more extensive a.nd more precise."'^ 



Professor Hall, '^^ in attempting to establish the distinctness of the two 

 gi'Oups, Portage and Chemung, uses these words: " When we apply the test 

 of organic remains, we find an equally, or even more strongly marked differ- 

 ence in the two gi'oups; and, upon this alone, a distinction between the 

 two should be made." In reporting upon the result of his examination 



132 Paleontologfe, 1. p 100. 



133 Contributions to the Natural History of the U. S„ vol. 1, p. 93- 

 "4 lb. p. 96. 



i-'Geolog. Kep. IVth Disf. N- Y., p. 229. 



