98 Hill — The Invertebrate Fossils of t lie 



two great formations of Texas, instead of in the middle of 

 the lower series, where it belongs. His original description of it 

 is as follows : 



Caprina Limestone. — Tliis is the uppermost recognized member of the 

 series and, although of no great tliickness, has a somewhat extended 

 geographical range. It is a yellowish-white limestone, sometimes of a 

 finely granular texture and sometimes made up of rather coarse, subcrys- 

 talUne grains, cemented with a chalky paste. It generally occurs in thick 

 massive beds, and is capable of withstanding the action of the weather to 

 a greater extent than most of the members of the Cretaceous system. 

 This formation is usually found capping the highest elevations, and its 

 presence may be nearly always recognized, even at a distance, by the 

 peculiar flat-topped and castellated appearance it imparts to the hills. 

 According to Dr. Riddell, it is finely displayed along the blufis of Brazos 

 river in Bosque, McLennan, and Hill counties ; also along the Leon and 

 Bosque rivers. The summits of the remarkable elevation known as 

 Comanche peak, in Johnson county, and that of Shovel mountain, in 

 Burnet county, consist of this rock. The fossils are chiefly Caj)rina, 

 Cytherea, and Ammonites of undetermined s])ecies. (Trans. St. Louis 

 Acad. Science, vol. i, 1860, pi^. 583-584.) 



In a previous paper the writer has described the Caprina lime- 

 stone substantiall}^ as follows : 



The Caprina Limestone. — Without any serious stratigraphic break in 

 the chalky limestones the abundant Comanche Peak fauna disappears 

 and there continue 300 feet, more or less, of chalks and chalky lime- 

 stones of varying degrees of consistency, from a pulverulent condition to 

 firm limestones, which seem to be a secondary condition of the chalk 

 produced by superficial hardening. These hard layers form the table 

 rock of the buttes and mesas of the extensive Grand Prairie region and 

 are exposed in the river bluffs between Austin and Mount Bonnell, on 

 the Colorado, where the chalk has been more or less hardened into fii'm 

 limestones by the local metamorphism accompanying faulting. The 

 lime-kilns and ciuarries immediately west of Austin are all located on 

 this subdivision. 



Accompanying these chalks and chalky limestones are well defined 

 layers of exquisite flint nodules, occupying ajiparently persistent horizons 

 in localities. The flint nodules are oval and kidney-shaped, ranging in 

 size from that of a walnut to about two feet in diameter. Exteriorly 

 they are clialky white, resembling in general character the flint nodules 

 of the English chalk clitfs. Interiorly they are of various shades of 

 color, from light opalescent to black, sometimes showing a banded struc- 

 ture. These flint nodules are beautifully displayed in sitn in the Deep 

 Eddy canyon of the Coloi-ado, above Austin, where they can l)e seen 

 occupying three distinct belts in the white chalky limestones. 



Wliere these chalky limestones form the basis of extensive plateaus, 

 such as the remnants of tiie (ii-and Praiiie west and southwest of Austin, 



