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prevailing forms:
- Ammonites vespertinus,
- Ammonites Marcyana,
- Pterodonta subfusiformis,
- Terebratula Wacoensis,
- Janira Texana,
- Lima Wacoensis,
- Cardium Sancti-Sabae,
- Trigonia (undt.),
- Gryphaea Pitcheri,
- and Hemiaster elegans
Near the base of one of the hills I observed layers of soft, thin-bedded, quartzose sandstone, about twenty feet in thickness. This rock is fine grained, of a light yellow color, and is conformable with the limestone. Thin seams of white gypsum and selenite were observed to occur at several points.
The surface of the valley is for the most part thickly strewn with coarse angular fragments of limestone, which are not unfrequently firmly cemented into calcareous breccia. Near the base of some of the hills this breccia often presents a thickness of twenty or thirty feet, and is of such extreme hardness as to be broken only with great difficulty.
Soil and sub-soil highly calcareous and barren.
Distance, 13 miles.
May 14.-Continued our way through the valley of the Pecos, encountering the same character of hills and cliffs as seen yesterday. The hills are often separated by wide intervals, and vary much in altitude, the highest of them being from six to eight hundred feet above the level of the Pecos. The cliffs are often deeply excavated, and at a distance present the appearance of a succession of hills. From their summits the table land may be seen stretching away for many miles, its surface everywhere broken and divided by rude rocky canyons.
The Cretaceous Limestone as observed to-day was found to vary considerably in texture at different points. In some places it was soft, earthy, and of a light yellow color; in other places hard, compact, and more or less crystalline. Owing to their unequal hardness the different beds weather in such a manner as to leave horizontal bands projecting sometimes several feet, which in the distance give to the cliffs the semblance of lines of fortifications.
The yellow fossiliferous band, above mentioned, was again met with during the day, but organic remains are much more sparingly distributed. In a few places beds of coarse yellowish and reddish quartzose sandstone were interstratified with the inferior layers of limestone in beds from ten to thirty feet in thickness.
The Rio Pecos as observed during the day presented an average width of about seventy-five feet, and flows over a hard rocky bed, with low bluff banks of red loam on either side. The water is highly charged with red sediment and impregnated with common salt.
Soil moderately fertile.
Distance, 11¾ miles.