38 RIO GRANDE COAL FIELDS OF TEXAS. [bull. iw. 
Four and one-half miles above the mouth of San Ambrosia Creek 
the following section was observed: 
Section 4 1-2 miles above mouth of San Ambrosia Creek. 
Feet. 
5. Fluvial silt, forming the top of the bluff. 
4. Ledges of soft, yellowish or whitish sandstone 7 to 8 
3. Laminated sandy clays, streaks of sand and streaks of clay. The colors are 
brown, yellow, and purple; the last being caused by carbonaceous matter. 3 
2. Soft sand bed of a light, grayish-purple color, with darkish sulphur-yellow 
patches 3 
1. Irregularly laminated soft sands, light grayish-green in color and containing 
much carbonaceous matter 4 
Total 18 
There is a considerable amount of soft, very pure sand rock along 
this part of the river. In No. 4 of the foregoing section the ledges 
sometimes change to thinly laminated sands along the face of a single 
exposure, as was observed in one instance. 
No. 1 of the section is quite thick, changing toward the base into 
clays of purplish color, due to the presence of carbonaceous matter. 
These beds are identical, in external appearance, with the lignitiferous 
Claiborne beds of Louisiana. They are probably 100 feet thick. 
It is at about the point where the foregoing section was made that 
the southern fence of the India ranch pasture is reached. This fence is, 
according to the statements of a colored cowboy, between three-fourths 
of a mile and a mile above the Webb-Maverick county line. Just beyond 
this fence, within the India ranch pasture, hematitic concretions con- 
taining Venericardia alticostata Conrad and a species of Glycymeris 
{Pectunculus) of the type of G. siaminea (Conrad), were found in the 
clays. A little farther up the river was a large mass of sandstone rest- 
ing on the clays and containing beautiful specimens of Turritella mor- 
toni. The sandstone was so hard that no attempt was made to get the 
shells out. 
From li to 2 miles above the fence referred to the thinly bedded 
sands and clays are seen to be underlain by thinly bedded sands, pass- 
ing downward into thin ledges of soft sandstone. 
This has carried the Eocene to a point at least 2 to 3 miles above the 
Webb-Maverick county line. The horizon of the Eocene is Midwayan. 
The following five species of fossils were collected: 
Turritella mortoni Conrad. 
Ostrea crenulimarginata Gabb. 
Glycymeris (Pectunculus) sp. indet. 
Venericardia planicosta Lam. 
Venericardia alticostata Conrad. 
Harris has identified, from the Dumble-Penrose collection made 3 
miles below the Webb-Maverick county line, fossils that are probably 
Midwayan, Lower Eocene, 1 but the writer has been unable to obtain a 
1 Durable: Jour, of Geol., Vol. II, No. 6, 1894, p. 550; Harris: Bull. Am. Pal., Vol. I, 1896, p. 127 
(No. 4, 13) . 
