12 BIOLOGICAL SOCIETY OF WASHINGTON. 



mie Group of our own country- Mr. Gardner would even extend 

 the application of this latter term so as to embrace all that series 

 of strata from the Dakota Cretaceous to the Laramie Group, inclu 

 sive. These terms, and the instances I have given of their appli 

 cation, are quite sufficient to show the existence of the facts to 

 which I have called your attention. But the following instances 

 of the early introduction and late continuance of certain import 

 ant types are of especial interest in this connection. 



From strata in Northwestern Punjab, India, which are by all 

 geologists admitted to be of Carboniferous age, a remarkable 

 collection of fossils was made which contained specimens of a 

 species of Ammonites. Upon the announcement of this fact its 

 truth was not only questioned by European paleontologists, but 

 some went so far as to deny the possibility of the association of 

 that genus with a Carboniferous fauna. Afterward the well- 

 known paleontologist Waagen visited the locality and himself 

 collected there specimens of Ammonites, Ceratites, and Go- 

 niatites, all associated together in the same layers with charac 

 teristic Carboniferous forms. 



That Goniatites should be found in Carboniferous strata was 

 to have been expected ; but if the Ceratites and Ammonites had 

 been found separately and unassociated with any other fossils, no 

 European paleontologist would have hesitated to refer the one to 

 the Triassic, and the other to the Cretaceous. In fact, Dr. 

 Waagen has placed the Ammonite referred to under a generic 

 group which is an especially characteristic one among Cretaceous 

 faunas. This instance of the commingling of types which are 

 characteristic of different periods is a remarkable one in all 

 respects, and especially as showing the very early differentiation 

 of even subgeneric forms, which are generally believed not to 

 have existed until a much later period. Confirmatory of the fact 

 of this introduction before the close of the Paleozoic age, of 

 types which are especially characteristic of the Mesozoic, Pro 

 fessor Heilprin has announced the discovery of an Ammonitic 

 form among a characteristic Carboniferous fauna from Texas. 



