INTRODUCTION. 



know in this geological period. We shall see, however, that the Coal 

 period, so important geologically, may in other regions be partially or 

 entirely destitute of this mineral, and not distinguishable by the usual 

 characteristics in which we ordinarily recognize the rocks of this period. 



The prevailing fossil species occurring in the calcareous bands of this 

 formation in its more easterly extension, are Spirifer camerattis*, S. lineatus, 

 Terebratula subtilita, T. millepunctataf, Produdus rogersi, P. semireticulatus, 

 etc. The species named are usually associated in all the localities examined 

 from Eastern Ohio to the Mississippi river. With the increase of calcare- 

 ous matter farther west, we find a larger number of species. In the collec- 

 tion made by Captain Stansburt on his route to the Great Salt Lake, in 

 the collections of the Pacific railroad explorations, and in those made by 

 Dr. R(EMER from Texas, as well as in collections from other sources, several 

 of the species cited above have been identified. 



At the same time, while these western explorations bring us from every 

 point marine fossils of the age of the Coal measures, there are no accom- 

 panying plants. Neither have any of these collections shown fossils of the 

 Lower Carboniferous limestones, or those which lie beneath the Coal 

 measures. All the fossils from the Rocky mountains, which have been cited 

 as the Lower Carboniferous limestone, have proved to be, so far as I know, 

 of species belonging to the period of the Coal measures ; and we are at 

 this time without evidence of the existence of the Lower Carboniferous 

 limestone in the Rocky mountains|. 



From a comparison of all the fossils which have come under my obser- 

 vation, I am forced to the conclusion, that the great limestone formations 

 which extend for long distances continuously in the Rocky mountains, 

 and which are known to extend from the limits of the Northern ocean to 



* Tbii tpeciei has been described by Dr. RaMCB ai S . meutebachanut (RdHEB, Kreid von Texas), and 

 by myself as S. triplicatui; while Dr. Owkn has identified it with S.fatcigerot Keyseblinq. It is undoubt- 

 edly the S. camtratui of Morton, which name has precedence over all the others. 



t It is possible that the species described as T. bovideni, by Dr. Mobtok, may undergo such variations 

 as to include forms like T. millepunctata. This cannot be decided, without a larger collection of speci- 

 mens than I possess at present. 



X See Report on the United States and Mexican Boiudary Surrey. 



