304 R. T. Hill — -Texas Section of American Cretaceous. 



"Caprina limestone," the "Comanche Peak Group," and the 

 "Caprotina " (Requiena) limestone, and his sections of Pack- 

 saddle Mountain, Burnet County, and Comanche Peak, Hood 

 County, will apply to this division wherever it is exposed, as 

 it is of great uniformity throughout. 



The buttes or mesas of Central Texas, where the best expo- 

 sures are found, locally rnistermecl "mountains" and "peaks," 

 are unique and peculiar to the region through which they are 

 distributed. They are low, truncated protuberances, usually 

 circular in outline. Their tops are invariably flat, and the 

 sides generally slope at an angle of forty-five degrees. They 

 seldom exceed three hundred feet above the surrounding level, 

 and are the most prominent landmarks of the region. The 

 chief of these are Comanche Peak, Hood County; Johnson's 

 Peak, Bosque County; Bound Mountain, Comanche County; 

 Santa Anna Peak, Coleman. County ; Kiowa Peak, Hardeman 

 County ; Castle Mountains, Tom Greene County ; Double 

 Mountains, on the head waters of the Brazos; Antelope Hills, 

 on the boundary of the Panhandle and Indian Territory ; 

 Packsaddle Mountain, Burnet County ; Church Mountain, Run- 

 nels County, and hundreds of others. In geological and general 

 features they are all alike, being remnants of a great formation 

 that once covered the whole region. Their simple structure 

 consists of perfectly horizontal deep marine sediments, the cap 

 stratum of which is the hard Caprina limestone of Shumard 

 (siliceous limestone of Roemer). This Caprina limestone occu- 

 pies a very low horizon in a Cretaceous section, and it is evi- 

 dent that structurally it is a plane of greatest resistance of the 

 Fredericksburg series, which covers, and was once covered by, 

 softer strata than its own. Most of them are situated in the 

 deep, worn river valleys, or around the edge of the Paleozoic 

 exposures. They usually stand upon a level prairie region of 

 limited extent, which are underlaid by thinner and firmer lime- 

 stones, constituting another plane of resistance. When the 

 latter is worn through, the Carboniferous, Jura-Trias, or what- 

 ever formation underlies the Cretaceous at the particular local- 

 ity, is soon exposed. The section of Packsaddle Mountain, 

 Burnett County, made by B. F. Shumard is almost identical 

 with the other buttes wherever I have examined them. This 

 uniformity over so wide an area is owing to the uniformity 

 of the sediments. 



The following fauna, which is a revision of that first pub- 

 lished by Roemer from Fredericksburg, and by Shumard from 

 the three synonymous divisions of his section, before men- 

 tioned, is found in this lower provisional division : 



