Wichita Mountains and Arbncklc Hills. — J^inglian. 49 
The Sedimentary Rocks. 
Ordovician. — ()n the nortli side of the plutonic axis of the 
mountains are hogbacks of hmestone dipping with a steep 
angle to the north. One of these hills northeast of Tymatee 
mountain was composed of about 340 feet of hard blue oolitic 
limestone, sometimes arenaceous and containing large quanti- 
ties of flint both in the form of sheets and nodules. The fol- 
lowing fossils were collected at this locality:* 
Rhaphistoma sp. • 
Ophileta complanata, var. nana. 
The data are scanty and inexact. The fauna represented 
is certainly Ordovician and may be Calciferous. 
One mile southeast of Fort Sill there is a quarry in a sandy 
argillaceous flaggy limestone. The following fossils were ob- 
tained at this locality: Paleophycus sp., IMurchisonia sp., 
Cyrtoceras sp., Lingttlella (?) cf. L. lam.borni, Asaphas (?) sp. 
These beds can be referred to the Ordovician, and may be 
as late as the Trenton. The relations to the Carboniferous 
are doubtful. 
According to the reports of Hill and Comstock there are 
Lower Silurian hills on the south side as well as on the north 
side of the axis of the mountains. 
x-Vccording to Lieut. Savill of Ft. Sill, the Rainy Creek- 
mountain is also composed of limestone. I did not go to this 
mountain, but from a distance it seemed to be composed of 
rock, apparently limestone, stratified in thick ledges. 
The hill two miles west of Mountain City is composed of 
arenaceous limestone dipping about two degrees north. I col- 
lected in this limestone poorly preserved casts of Modio- 
morpha or Modiolopsis. The specimens are too poor for de- 
termination, and we cannot ascertain the age of this limestone 
more definitely than that it is Paleozoic. 
Permian: The southward facing escarpment north of the 
valley on the north side of the Wichita mountains is composed 
of red beds that are Permian. The Permian is also exposed on 
the south side of the north fork of Red river in the vicinity of 
Stittle mountain. Here the base of this formation is composed 
of an arkose evidently derived from the disintegration of the 
*A11 of the paleontologic determinations are by Dr. G. H. Girty. 
