84 RIO GRANDE COAL FIELDS OF TEXAS. [bull. 164. 
STRATA BELOW THE SAN CARLOS FORMATION. 
About Qi miles from Chispa, along the Rio Grande Northern Rail- 
road, there is an exposure of thinly laminated bluish calcareous shale, 
containing Inoceramus labiatus, Placenticeras sp., and Ptychodus sp. 
These shales represent the Eagle Ford shales and the Valverde flags 
of eastern and central Texas, and the Benton shales of the western 
interior region. 
Running subparallel to the railroad, on its west side, is a ridge 300 or 
iOO feet above the roadbed. Along the eastern foot of this ridge the 
Benton shales are exposed; they have a dip of 7° or 8° S. Three 
hundred feet above the railroad, near the summit of the ridge, a lime- 
stone with a rather steep westerly dip, and containing a fauna appar- 
ently of Washita age, is exposed. The Benton shales have been faulted 
several hundred feet below the Washita. 
A section up the side of this ridge was as follows : 
Section of ridge about 6 1-2 miles from Chispa, on Rio Grande Northern Railroad. 
(Pi. XI, fig. 3.) 
Feet. 
4. Alternating ledges of hard nodular or soft nodular limestone, the nodules con- 
taining numerous fossils. 
3. Flaggy brown sandstone. 
V. Ledges of massive limestone, hard, bluish, weathering brown, much jointed, 
weathered surface very rough, fossiliferous. Contains silicious or cherty 
nodules in which were found Radiolites, Requienia, Monopleura, and Pho- 
ladomya 25 
I. Nodular, argillaceous limestone, fossiliferous, resembling in lithologic aspect 
the Comanche Peak limestone of central Texas. 
The following fossils were collected from the foregoing section : 
Fossils from No. 4 {field No. 303) . 
Enallaster texanus Roemer. 
Holectypus planatus Roemer ? 
Kingena wacoensis (Roemer) . 
Neithea texana Roemer. 
Cypricardia texana Roemer? 
Cinulia sp. 
Chemnitzia ? sp. 
Ammonites sp. 
Apparently this fauna is of Washita age. Kingena wacoensis is usu- 
ally a Washita species, though it also occurs in the Edwards limestone. 
Fossil from No. 2 {field No. 803a). 
Ichthyosarcolithes anguis Roemer? 
This bed is referred to the Edwards limestone. 
Fossils from No. 1 {field No. 303b). 
Gryphsea sp. 
Neithea texana Roemer. 
Pleuromya knowltoni Hill? 
Turritella seriatim-granulata Roemer? 
Tylostoma pedernalis Roemer. 
