894 Mesozoie Rocks of Colorado. — Stevenson. 
south of the Colorado line, where the Dakota overlaps the 
Carboniferous rocks there exposed, and rests on Archaean. 
Red rocks re-appear under the Dakota at about 30 miles 
further south, not far above the village of Coyote on Coyote 
creek. Thence these rocks were followed southwardly for 
nearly 40 miles to Bernal hill and thence westwardly to Gal- 
isteo creek. They have a narrow outcrop at the base of the 
Dakota bluffs, owing to the rate of dip, the width of the ex- 
posure being so small that it can be represented only by a 
line on a map with scale of one inch to four miles. These red 
rocks of the Dakota bluff, so distinct along the old stage road 
from Pecos river to Galisteo creek, are those which the writer 
referred to the Trmss?'^' and they are the TWrt-S's/cof Mr. Marcou. 
The great mass of Irias and Jurassic more than 2,500 feet thick 
near Canon City, Colorado, is unrepresented along the line 
examined from not less than 20 miles north of the New Mexi- 
can boundary to fully 60 miles south of that line ; thence 
southward and around the southern extremity of the Spanish 
Ranges, tlie thickness does not exceed 700 feet. No fossils 
were seen in these beds by the writer, but near Las Vegas, 
New Mexico, Dr. Hayden found a Modiola of Jurassic type. 
Now let us return to the Dakota. The sandstone, which in 
central Colorado lies between the Fort Benton beds above, 
and the Jurassic beds below is known as the Dakota. The 
thickness is not far from 250 feet near the New Mexico line, 
where the mass appears to consist of two plates of sandstone 
separated by softer material not well exposed; the " Stone- 
wall " of Dakota usually shows a notch along the crest, but 
tlie character of this middle material is nowhere shown in de- 
tail, though at one locality there is evidence that a limestone 
is present. This is the condition certainly as far as to 15 
miles south of the New Mexico line, where the overflow of 
eruptive rocks puts an end to the exposure and the Dakota is 
not shown again for 15 miles or until the Moreno valley is 
reached near Elizabethtown, where it rests on the Archaean 
and the Niobrara is shown above it. There the triple division 
is well exhibited ; and this feature becomes more and more 
marked from this locality southward. The thickness increases 
rapidly so that the section, which showed less than 300 feet on 
the Purgatory river in Colorado, shows on the waters of the 
Mora river. 
