Geologic Story of the Colorado River. — Hill. 287 
1883 — Descriptions of Fossils from the Cincinnati Group — Journal of 
the Cincinnati Society of Natural History, vol. 6, pp. 235, 236. 
Two new species described, with one plate. 
1884 — Description of three species of Fossils, — Jour. Cin. Soc. Nat. 
Hist., vol. 7, pp. 20-24. With illustrations of species described. 
1884 — On Conodonts and Fossil Annelid Jaws, — Jour. Cin. Soc. Nat. 
Hist., vol. 7, pp. 143-150. Four new species described ; one plate. 
1884 — Descriptions of four new species of Fossils from the Cincinnati 
Group,— Jour. Cin. Soc. Nat. Hist., vol. 7, pp. 1.37-140. With a 
plate. 
1885 — Glyptocrinus P.aeri, ]\Ieek, — Jour. Cin. Soc. Nat. Hist., vol. <S, 
p. 71. Note on fine specimen. 
1887 — Genus Agelacrinus, Vanuxem (mis-printed Agelacinus), — Jour. 
Cin. Soc. Nat. Hist., vol. 10, p. 25. One species described and 
figured. 
1887-1888 — On the Monticuliporoid Corals of the Cincinnati Group, 
with a critical revision of the species, by U. P. James and Joseph 
F. James, — Jour, of the Cin. Soc. Nat. Hist., part 1, vol. 10, pp. 118- 
141; part ii, same Journal (1888) vol. 10, pp. 158-184, with one 
plate; part in, same Journal (1888) vol. 2, pp. 15-44; one plate. 
Descriptions of 64 species and six varieties; one new one. 
A PORTION OF THE GEOLOGIC STORY OF THE 
COLORADO RIVER OF TEXAS. 
By Robert T. Hill. 
Often have I scanned the topographic maps of this little 
known south-western region, pondered over the peculiar bends 
and meanderingsofits rivers and endeavored to create hypothe- 
ses for their vagaries. The past year has afforded opportunities 
to study most of these from the Mississippi to the Rio Grande. 
All were interesting in their relation to topography and form- 
ation, but the Colorado of Texas presented the most interest- 
ing features, rivaling in some respects those of its world- 
famed name-sake, the Colorado of the West. 
The Colorado begins in the dry arroyas which border the 
eastern scarp of that great plateau, the Staked Plains of Texas. 
These caiions, cut nearly a thousand feet perpendicularly in 
the soft Quaternary, Cretaceous, Triassic (?) and Permian 
strata, which record in their precipitousness both the aridity 
and the gradual elevation of the region. Plowing eastward 
through the Red beds, Permian and Triassic, across the strike 
of the formations, the middle third of the river is reached be- 
tween the 97th and 98th meridian. Here the Colorado cuts 
through the area of paleozoic rocks which has been the land 
barrier between the Atlantic ocean and the inland sea during 
numerous oscillations which have marked the neozoic history 
