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Near the town of Preston, and at a number of localities between that place and the Upper Cross Timbers of Texas, it is soft, highly argillaceous, and crumbles rapidly on exposure to the weather.

On the Big and Little Witchita and Upper Brazos Rivers, it is hard, thin bedded, and of a dull light gray color, while along the Upper Red River it becomes more or less arenaceous, often passing into pure sandstone, which not unfrequently contains numerous nodular concretions of iron.

Farther south, along the route traveled by our Expedition between Victoria and San Antonio, and at various points west of the first crossing of the Rio Pecos, it is dull white, soft, and resembles pulverized chalk. At San Antonio, Fort Inge, and Fort Clarke, it is white or light gray, earthy in texture, and quite soft when first taken from the quarry, but possesses the valuable property of hardening upon being exposed for a short time to the action of the weather.

On the Rio Seco it is a dull white, soft, and cannot be distinguished from chalk. On the Arroyo Pedro it is of a light fawn color, compact, and breaks with a conchoidal fracture.

At several localities between San Antonio and San Pedro or Devils River it is a buff, compact calcareo-magnesian limestone. Between the San Pedro and Pecos Rivers it, is sometimes hard, ferruginous, and contains a great abundance of flints, while in other localities it is more or less arenaceous, and at times passes into a pure sandstone.

Near the mouth of Delaware Creek it is a hard limestone, full of small, rounded cavities, and of a light cream color; but towards the sources of that stream the strata are thin bedded, of a light gray color, and appear to be undergoing rapid disintegration. South of this stream they are both compact and porous and sometimes crystalline.

PALEONTOLOGY.

Many of the organic remains such as collected by your Expedition from the upper division of the Cretaceous System have been described by Dr. Ferd. Roemer in his excellent and finely illustrated work on the Cretaceous Strata of Texas. We are able, however, to considerably augment the list by the addition of a number of new and interesting forms, which have been placed in the hands of a paleontologist for examination and description. We will, therefore, at present merely enumerate some of those species which have been found most characteristic of the mass.

The following species have been found to range from the top to the base of the formation:

• Gryphoea Pitcheri (Morton),
• Exogyra arietina (Roemer),
• Janira Texana (Roemer sp.),
• Janira quadricostata (Sowerby),
• and Terebratula Wacoensis (Roemer).

In the upper part of the formation we find most commonly the following, and as far as our observations extend they are peculiar to it:

• Ceratites