OF NORTH AMERICA. 
21 
and P. jjyxidiformis ; Terebratula pkmo—sukala; Spirifer lineatus , S. strialus\ Amplexus coralloides ', Zaphrentis 
Stamburyi: all fossils very characteristic of the Mountain Limestone of Arkansas, Missouri, Iowa, 
Illinois, Indiana, Kentucky, Tennessee, Virginia and Pensylvania, as well as in Europe, and 
even in Asia, Australia and South America. 
We have not met upon our route with beds of coal; but the presence of the Black Slate be- 
tween the Mountain Limestone and the red clay of the Trias , indicates the existence of beds of coal 
on several points of the Rocky Mountains; and, in effect, the inhabitants of New Mexico pointed 
out to me, in several places, beds of bituminous coal belonging, without any doubt, to the rocks 
of the Coal Measures. 
On quitting the last beds of limestone that rest upon the Quartzose Metamorphic Rocks, we find 
Serpentine-, then we come upon masses of Granite, which form the centre of the line of dislocation 
I 
i’ 
Santa Fe ; and the 8"' October I started with my friend Dr. John Bigelow', the botanist of the expedi- 
tion , to ascend the highest peak of the Sierra de Sandia. The Geological Profile w'hich accompanies my 
Geological Map of North America was arranged from the observations made in this excursion, during which 
I saw several times the superposition of the Cretaceous Rocks upon the Jurassic formation with discordance of 
stratification ; the superposition with concordance of the Jurassic Rocks upon the New Red Sandstone ; all the 
divisions of the New Red Sandstone being superposed upon each other in the most clear and incontestable man- 
ner ; then the strata of the New Red superposed in concordant stratification upon the Black Slate of the Upper 
Carboniferous or Coal Measures , and below the Carboniferous Limestone resting upon Metamorphic Rocks, and 
these last upon Granite. ' 
In this exploration, which continued until the 20'*' October, I studied with attention the rocks of 
San Antonio Pass, of Antonito and of the Summit of the Sierra de Sandia, also those of the environs 
of the villages of San Pedro, Tuerto, Galisteo and Pecos. The ascent of one of the most elevated Sum- 
mits of the Rocky Mountains, — which after all is not a very easy matter, considering the wilderness, 
the difficulty of the roads and the fear of the Apache Indians — w'as effected by Dr. Bigelow and my- 
self the 10"' of October 1853. We chose the most elevated point of the Sierra de Sandia seen from 
.Albuquerque, which attains the height of 12,000 feet above the level of the sea. The culminating points 
of all this Sierra are composed of Carboniferous Limestone, which here merits most truly its name of Moun- 
tain Limestone, for it is the only limestone of any importance met with in the Rocky Mountain region. 
From the five or six upper beds, I collected the following fossils: Productus Cora, P. scabriculus , P. 
Flemingii ; Zaphrentis cylindrica , Z. Stansburyi and Orthoceras Nova—Mexicana. 
In going from Albuquerque to San Antonio , in the middle of the Pass or Canon of San Antonio, ten 
minutes from the village of Tigeras, there is a bluff oi Mountain Limestone on the right of the road, form- 
ing a grand perpendicular wall. Fossils abound in the strata of this bluff, and I collected the following 
species: Productus semi-reticulatus , P, Cora, P. Flemingii, P. punctatus , P. pustulosus , P. pyxidiformis ; 
Terebratula plano-sulcata , T. subtilita ; Spirifer lineatus , S. striatus , S. Rockymontani ; Amplexus coralloides 
and Zaphrentis Stansburyi. 
Finally at the village of Pecos, where the valley is reduced to a deep gorge, giving- passage only 
to the river and the road, the rocks of the Mountain Limestone are very much developed and extremely 
rich in fossils. On the left side of the river especially there are strata composed entirely of Spirifer, 
Productus and Terebratula-, the most common species I found are the following : Productus semi-reticulatus 
P. Cora and P. scabriculus-, Terebratula subtilita, T. Rockymontana; Spirifer triplicata, S. striatus-, Ortho i 
Pecosii ; Myalina Apachesi -, Amplexus coralloides. 
The mean thickness of the Mountain Limestone of the Rockx' Mountains in the region environinf 
Santa Fe and Albuquerque is 700 feet. 
