30 RIO GRANDE COAL FIELDS OF TEXAS. [bull. 164. 
of the rocks, and the stratigraphic position of the Exogyra costata 
clays and their associated sand beds seems to coincide with that of the 
sands and clays forming the top of the escarpment overlooking the Rio 
Grande Valley, 6i miles north of Eagle Pass, i. e. , the base of the 
Escondido formation. These beds occur considerably above the coal- 
bearing horizons. About 2 miles from the court-house is a fossilifer- 
ous horizon in clays, a section of which gives the following : 
Section 2 miles north of Eagle Pass court-house. 
Feet. 
4. Hard brownish sandstone ledge, forming top of the escarpment, 
3. Slope of soft yellowish sandstone, about 20 
2. Indurated fossiliferous layer £-1 
1. Yellowish clay. 
Mr. Stanton has determined the following from a collection of fossils 
made at this locality : 
Cardium eufalense Conrad? 
Mactra sp. Cf. Mactra formosa M. and H. 
Dentalium sp. 
Natica sp. Occurs at Kaufman, Texas. 
Turritella winchelli Shumard. Occurs at Corsicana, Texas. 
Strepsidura ripleyana Conrad. 
Undetermined volutoid? Cf. Ancilla cretacensis Conrad. 
Volutomorpha sp. Cf. V. gabbi Whitefield. 
Sphenodiscus pleurisepta (Conrad) . 
The conclusion to be drawn from these notes is that the whole of 
the rocks exposed from the crossing over Chacon Creek to Eagle Pass 
belong above the Eagle Pass coal and correspond approximately to the 
base of the Escondido formation. 
RECONNAISSANCE FROM EAGLE PASS TO CARRIZO SPRINGS. 
From Eagle Pass to Robert Thomson's house, 20 miles east of the city, 
the bed rock presents the same character that it exhibited in going 
down the Rio Grande to Santo Tomas. It consists of sandstone and 
clays; for the last 8 miles before reaching Thomson's ranch clays pre- 
vail. The tops of the hills are generally capped by gravels, the sand- 
stone and clays being exposed in the creek valleys and along the 
slopes. 
Four miles east of Thomson's, on the road to Carrizo Springs, a 
specimen of Sphenodiscus pleurisepta was found in yellow clays. 
To within 9 miles east of the Thomson place dirty, dark ocher-colored 
clays form for the most part the surface of the ground; there is some 
sand in the draws, and gravels occur on the high ridges. No sharp line 
between the Cretaceous and Eocene was discovered, and no fossils were 
found in the transition beds. 
At about 9 miles east of Thomson's ranch and 16 miles west of Carrizo 
Springs, a ckange of geological formation was noticed. The clays above 
