28 MALONE JURASSIC FORMATION OF TEXAS. [bull. 26j 
Sierra Blanca station, and in Bluff and Yucca mesas near the sanit 
station, but I was unable to confirm these correlations. The strat: 
in the " Etholen Knobs " may possibly belong here, but the othe: 
localities almost certainly show only Cretaceous beds. 
THE CRETACEOUS. 
Cretaceous rocks have a great development in this region an* 
represent the three main divisions of the Comanche series — tin 
Trinity, Fredericksburg, and Washita — as well as a part of tin 
Upper Cretaceous. Lithologically the section differs greatly t'ron 
that of Central Texas, where the Comanche series lias been most- 
studied, and there are also considerable differences in the vertica 
range of some of the common species, so that it is impracticable to 
recognize many of the minor formations and horizons that havo 
been studied. The general fauna] succession is the same in botli 
regions, and it is usually not difficult to classify the beds by mean; 
of the fossils as Trinity. Fredericksburg, or Washita, though it \va; 
difficult and sometimes impossible to assign each exposure to fl 
exact position in the general section, because many of them are relajn 
tively small and isolated, and the structure is complicated by foldsH 
faults, and igneous intrusions. The most complete sections are tc< 
be found in the Quitman Mountain-, especially toward the southern 
end and in the lower hills farther south on the Rio Grande, in the 
southern extension of the same line of uplift. 
Quitman Mountains. — This range begins at a point on the railroad 
8 miles west of Siena Blanca station and extends in a southeasterlj 
direction about 25 miles, the uplifted beds continuing as low ridges ii| 
the same direction and crossing the Rio Grande 6 or 7 miles beyond 
the end of the main range. At its northern end it is composed inainlr 
of igneous rocks — granites and porphyries — with Cretaceous beds iiji 
the adjacent foothills on the north and east, but south of Quitmanl 
Canyon, a drainage channel that cuts straight across the range abouli 
10 miles south of its northern end. the mountain mass is composed of 
Cretaceous sediments, with only occasional igneous intrusions. The 
axis of the range is for a number of miles almost parallel with the llii 
Grande, which flows about 6 miles to the southwest, while on the other 
side is the flat valley of Quitman Arroyo, 4 to 10 miles wide, separaji 
ting the Quitman Mountains from Devils Ridge and Eagle Mountain!! 
Sections taken at different points across this range vary greatly in 
extent. The one published by Taff in the report cited was takefl 
near Quitman Canyon (Section III of map), and shows the strati 
with variable steep dips mostly to the west, but sometimes reverses 
Near the eastern end of the section is a heavy bed of limestone, form 
ing part of Taff's " Bluff bed," filled with Orbitolina texana and a 
