38

Four and one-half miles above the mouth of San Ambrosia Creek the following section was observed:

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 containing Venericardia alticostata Conrad and a species of Glycymeris (Pectunculus) of the type of G. staminea (Conrad), were found in the clays. A little farther up the river was a large mass of sandstone resting on the clays and containing beautiful specimens of Turritella mortoni. The sandstone was so hard that no attempt was made to get the, shells out.

From 1½ to 2 miles above the fence referred to the thinly bedded sands and clays are seen to be underlain by thinly bedded sands, passing 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, but the writer has been unable to obtain a "

Dumble: Jour. of Geol., Vol. II, No. 6, 1894, p. 550; Harris: Bull. Am. Pal., Vol. I, 1896, p. 127 (No. 4,13).