INTRODUCTION. 
63 
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 cameratus*, S. lineatus, 
Terebratula subtilita, T. mill epund at of , Pro ductus 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 Stansbury 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 
* This species has been described by Dr. Rcemee as S.meusebachanus (Rcemee, Kreid von Texas), and 
by myself as S. triplicatus; while Dr. Owen has identified it with S.fasciger of Keyserling. It is undoubt¬ 
edly the S. cameratus of Morton, which name has precedence over all the others. 
t It is possible that the species described as T. bovidens, by Dr. Morton, 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. 
$ See Report on the United States and Mexican Boundary Survey. 
