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Contributions to the Geology of Texas. 21 
Art. Il.—Contributions to the Geology of Texas; by Dr. 
Ferpmanp Roemer. 
Ar the time when I wrote the short sketch of the geology o: 
Texas, contained in a previous number of this Journal,* I had 
seen only a comparatively small portion of the country. I have 
- since extended my observations over a much larger surface and, 
profiting by some peculiarly favorable circumstances, I have 
become acquainted with sections of the country generally con- 
sidered inaccessible on account of the dangerous character of the 
Indian tribes by which they are inhabited. 
I have collected a sufficient number of facts for a geological 
map of the whole state, which will be true at least in all its gen- 
eral features. My collections of fossils will serve to test the 
correctness of the observation and the inferences drawn from 
them. They contain a considerable number of new forms, 
chiefly from the cretaceous formation, which require to be de- 
At present I wish only to present a short account of the gener- 
al results which I have derived from my geological survey of the 
country. 
An ideal line drawn from Presidio de Rio Grande on the Rio 
Grande in a n.£. direction, and crossing the San Antonio River at 
the town of the same name, the Guadaloupe at New Braunfels, 
(the German settlement,) the Colorado at Austin, the Brazos at 
the falls of this river, the Trinity below its forks, and reaching 
from there to the Red River in the same n.r. direction, divides 
the tertiary strata and the diluvial and alluvial deposits (of the 
level and “rolling” part of the country) from the cretaceous and 
older formations (of the hilly and mountainous sections). 
The few remarks to be made about the former region, are first 
that the tract of level country which extends like a broad belt 
along almost the whole coast of Texas, is diluvial and partly 
alluvial in character. Its small elevation of a few feet only above 
the level of the sea, and its perfectly level surface, indicate, at 
once, the recent origin of the soil. The fossil remains, found in 
many places in the deposits of clay and sand, prove their modern 
age still more conclusively. At the head of Galveston bay and 
even near the town of Houston, I found at a height of twelve to 
twenty feet above the general level of the bay, large deposits of 
shells of Gnathodon, a bivalve mollusc, which lives abundantly 
in the brackish waters along the coast of the Mexican Gulf, 
in the bay of Galveston particularly. Some few oyster shells of 
the common kind occur in these deposits of half fossil a 
* Volume ii, ii Ser., p. 358. 
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