362 A Sketch of the Geology of Texas. 
On the other side of the Guadaloupe, the limestone is exposed in 
many places on the road from New Braunfels to San Antonio, 
which leads in a southwestern direction. Where the road. cross- 
es the Cibolo, the limestone forms in the bed of the river singular- 
ly shaped rocks, through which the water has eaten its channel, 
and which are teeming with fossils. At San Antonio the lime- 
stone is opened by several stone quarries, and the far famed Ala- 
mo mission has been built of it. West and south of San Anto- 
nio, I have not yet seen the limestone myself, but I have reason 
to believe that it extends much farther in both directions. A spe- 
cimen of the same Exogyra which abounds on the Guadaloupe, 
was brought to me and said to have been found anni the peb- 
bles in the bed of the Rio Grande. 
Besides this white marly limestone, there is anothiie-d series of 
strata to be described.. Ascending, from New Braunfels, the range 
of steep hills which stretches to the northwest of this place, as 
soon as you leave the level of the valley, horizontal strata of a 
compact yellowish limestone are seen, resembling very much the 
compact limestone of Italy, and of Southern Europe in general. 
Some of the strata are very siliceous, containing large compress- 
ed nodules of pure dark colored silica. Other. beds are so soft 
that they easily decompose through the action of air. Where 
limestone is very compact, hardly any trace of fossils is seen in 
it, but some of the looser strata abound with shells. Among 
them there is a small species of Exogyra, which for its promi- 
nent, spiral beaks and general shape might easily be mistaken 
or a species of Chama or Diceras; it is very common, and in 
some localities oecurs in great abundance. ‘Together with this 
Exogyra, there is in most places a new species of Gryphea; al- 
so a smooth and globose Terebratula, and occasionally a specimen 
of Pecten quadricostatus: These beds of soft marly limestone 
are not only seen every where on the mountains in the neighbor- 
hood of New Braunfels, but they extend north of this place about 
seventy miles as far as to the Piedernales river, every where con- 
‘the same fossils. Over the same wide range, there are 
ethic fossiliferous strata of an entirely different character. I saw 
them first in a deep ravine near the narrow rock-bound channel 
of the Guadaloupe, eight miles north of New Braunfels. One 
thick bed of compact limestone contains, in immense numbers, 
certain organic bodies. of cylindrical shape. These fossils are 
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