Mesozoic JRocks of Colorado. — Stevenson. 391 
careful and extended researches in this branch of paleontology. 
The fine cast of the interior, which made a diagnosis of the 
genus possible, belongs to his collection. Other specimens 
are in the author's cabinet. 
Formation and locality/ : This species is associated with 
fossils marking the upper beds of the Cincinnati group, at 
Wilmington and Savannah, 111. 
( To be Continued. ) 
THE MESOZOIC ROCKS OF SOUTHERN COLORADO AND 
NORTHERN NEW MEXICO. 
By John J. Stevenson. 
The mesozoic section along the easterly foot of the Rocky 
mountains from central Colorado southward has been studied 
more or less, by numerous geologists. In 1869, Dr. Hayden 
made a reconnaissance of the whole line from Denver to Galis- 
teo creek, making connection with the work of professor 
Marcou and the later work of Dr. Newberry. The writer fol- 
lowed the same line, studying somewhat closely in 1878 the 
area between Cucharas creek in Colorado and Las Vega& in 
New Mexico, and making reconnaissance examinations of the 
region between Denver and Cucharas in 1873 and of that from 
Las Vegas to Galisteo creek in 1879. The portion of the line 
within Colorado was studied by members of Dr. Hayden's 
corps. Mr. St. John has given an admirable description of 
the upper Canadian area in New Mexico ; Dr. Newberry fol- 
lowed the southern portion from Leavenworth crossing of the 
Canadian to Santa Fe along the Santa Fe road ; and Prof. 
Marcou touched it during an excursion northward to Galisteo 
and Pecos. 
The mesozoic section in central Colorado shows the follow- 
ing succession : 
Cretaceous. 
Laramie. 
Fox Hills. 
Fort Pierre. 
Niobrara. 
Fort Benton. 
Dakota. 
Jurassic . 
Triassic. 
The top of the Laramie is not reached near the foot of the 
