60

supposed to be a hundred and fifty years old, has suffered comparatively little from decay, and is still used as a place of public worship. Near its upper portion the rock is often filled with dark nodules of flint, sometimes arranged in nearly parallel bands, varying from a few inches to a foot in thickness, but more frequently they are scattered promiscuously through the layers, and often so numerously as to form coarse conglomerate.

Many of the layers are highly fossiliferous; indeed, some of them are almost wholly composed of Ostrea (Exogyra) lceviuscula. The fossils are usually in a good state of preservation and may be readily detached from the matrix. The most common species are Ostrea loeviuscula, Ostrea Pitcheri, Ignoramus Crispii, Cardium elegantulum, and Ammonites.

A second variety of limestone, somewhat extensively quarried about one mile east of San Antonio, corresponds lithologically with the soft limestone so frequently encountered on our route from Victoria, and although somewhat largely employed in the neighborhood as a building material, possesses but little durability and will yield readily to the weather. It is so soft that it crumbles readily between the fingers, and resembles the softer varieties of chalk.

Still another kind, occurring however much less abundantly than either of the above, is a hard compact variety. It was only observed in detached fragments, strewn over the surface. I was unable to find the beds from which it was derived.

In one place a local deposit of soft porous limestone was observed, which, from its containing impressions of the stems and leaves of cedar trees and other existing plants, is evidently of very recent origin.

The following section will explain more fully the relative position, and as far as could be ascertained the thickness of the different strata composing the formation as observed in this vicinity:

• No. 1. Flint nodules and rolled fragments of limestone. Thickness, 15 feet.
• No. 2. Soft and hard white chalky limestone, containing flints and numerous fossils. Thickness, 200 feet.
• No. 3. Soft chalky limestone. Thickness, 25 feet.
• No. 4. Indurated blue and yellow marly clay, with thin bands of sandstone interstratified, and a thin seam of selenite. Thickness, 150 feet.

The bed (No. 4) of this section has been artificially excavated to the depth mentioned without reaching the base of the formation.

I have received from a gentleman residing in San Antonio specimens of Exogyra costata and Inoceramus Crispii, which were procured from the clay at the bottom of this well.