52 The American Geologist. July, is9'.> 
Wild Horse creek and the Washita river for about forty miles, form- 
ing an almost impassable barrier for wagon travel.*" 
The Arbucklc hills are not jagged precipitous mountains 
like the Wichitas but are gently rounded hills. Looking south 
from Arbuckle, it can be seen that the tops of the hills are tim- 
ber-covered. On the north side of the summit is a strip of 
prairie country. Outside of this prairie belt is more timber 
when the sandy Carboniferous strata come in, and along the 
bottoms of the creeks. 
Geology. 
Tishomingo granite.- — South of Boggy P. O. in the Choc- 
taw Nation, is an extensive area of granite, described by Hill, 
under the name of the Tishomingo granite. This granite, 
lithologically, is a muscovite, biotite granite and is very differ- 
ent from the hornblende granites of the Wichita mountains re- 
ferred to previously. The Tishomingo granite is overlain by 
limestone, apparently of Silurian age. No evidence of the in- 
trusion of the granite could be found, and it seems most prob- 
able that the limestone has been deposited on the surface of 
the granite. 
Lower Silurian (Ordovician). A hard gray or bluish, 
coarse-grained limstone forms low hills on the south side of 
Boggy creek, eight or ten miles above Stonewall. From this 
locality the following fossils were collected: Orthis (Plesi- 
omys fontinalis) White, Asaphus sp. (fragments), Bellero- 
phon sp. 
These strata can be referred to the lower portion of the 
Ordovician. Orthis fontinalis was described from strata of the 
age of the Quebec group. 
Upper Silurian. The Lower Silurian limestone is overlain 
by flaggy cherty limestone. In one of the cherts a specimen 
of Strophonella was found. These cherts can probably be cor- 
related with a series of beds, described by Mr. Hill in a publica- 
tion later referred to, which furnished fossils identified by 
Prof. H. S. Williams as probably of Lower Helderberg age 
(p. I2i). Collections subsequently made from an extension of 
this series into Indian territory show" a varied and character- 
istic Lower Helderberg fauna. 
*Am. Jour. Sci., 3rd Ser., vol. XLII, p. iig, 1891. 
