64 GUIDEBOOK OF THE WESTERN UNITED STATES 
empties into the Gulf of Mexico at the head of San Antonio Bay. 
Although there is a wide alluvial plain adjoining the river, formations 
of Upper Cretaceous age are extensively exposed at intervals in its 
banks and adjoining slopes. The uppermost of these is the Navarro, 
which consists almost entirely of dark clay from 400 to 500 feet thick, 
with some beds of sand and layers of calcareous concretionary sand- 
stone and impure limestone. In this general region the Navarro 
formation dips somewhat less than 1° E. The clay is quarried exten- 
sively in pits near the river bank about a mile south of the bridge 
across the Guadalupe River at the village of McQueeney and is made 
into brick and tile used in San Antonio and other places. Ordinarily 
in the manufacture of such products a pure clay, which melts at a 
moderate temperature, has to be tempered by mixing with sand, but 
at this place there is sufficient sand or sand admixture to afford suit- 
able composition to withstand the requisite heating in the The 
exposure comprises a bank about 100 feet high and a pit 50 feot deep. 
Fossils “ are abundant in the lower part of the pit. 
From the Guadalupe River to San Antonio the railroad traverses 
a region of slightly rolling plains of low relief developed in the soft 
clays of the Navarro and Taylor formations, here 
Marion. about 1,300 feet thick and dipping gently to the south- 
Population 0 east. Outcrops are few and small, for soil and super- 
ew Orleans 548 miles. ficial materials cover most of the surface, and much of 
the land is under cultivation. The mesquite is very 
prominent in the untilled fields. Southeast of Schertz a large gravel 
pit in the alluvial deposits on the Cibolo River is visible from the 
railroad. To the west is a hilly country of Austin chalk, and beyond 
is the highland known as the Balcones scarp (bal-co’nace), formed of 
the hard limestones of the Lower Cretaceous (Comanche series), which 
there rise to the surface on the general southeast dip of all the strata 
of the Coastal Plain region, the uplift increased in places by faulting. 
The Upper Cretaceous strata (Gulf series) crop out in a wide zone 
along the inner margin of the Coastal Plain, which extends through 
Fort Worth, Dallas, Waco, Austin, and San Antonio. They are 
underlain by the formations of the Comanche series, which constitute 
the high uplands to the west and north. The table on page 65 shows 
the general succession and principal features. 
* A few of the better-known fossils | Pulvinites argentea, Crenella_ serica, 
that occur in the Navarro formation in | Liopistha protexta, Veniella conradi, 
this area are Leda longifrons, Gryphaea | Cyprimeria alta, Legumen ellipticum, 
mutabilis, Exogyra costata (variety with | Gyrodes petrosus, and Sphenodiscus (two 
narrow costae), Gryphaeostrea vomer, | or more species). (L. W. Stephenson.) 
