ujghan.] UPPER CRETACEOUS FORMATIONS. 19 
bper or more calcareous, sometimes arenaceous, horizons (called 
fish beds" by Shumard, Hill, and others) persist, becoming more 
scentuated. 
The local name "Valverde flags" 1 has been proposed for these beds 
long the Rio Grande, but there is not sufficient Lithologic difference 
> warrant the use 4 of a separate designation, and the equivalence of 
[e Valverde flags and the Eagle Ford beds has, as stated, been estab- 
shed by actually tracing the beds across the area intervening between 
ie areas to which the two names were originally applied. 
Outcroppings of the Eagle Ford flags were seen along the road from 
>el Rio to Eagle Pass, from a point 3 miles southeast of the former 
lace until the valley of Sycamore Creek was reached, where they 
fere obscured by the debris in the valley. The distance across the 
:ea of exposures is about 8 miles. 
No estimate was obtained of the thickness of this formation in the 
icinity of Del Rio. Bumble has estimated that it is 600 feet thick. 2 
ear Brackett it is about 250 feet thick, by actual measurement, so 
lat it would seem that the foregoing estimate is probably too great. 
AUSTIN CHALK. 3 
This formation is a soft, chalky, argillaceous, white limestone, con- 
ining a little ferruginous matter in the shape of pyritiferous lumps 
I nodules of marcasite. Sometimes there are alternations of chalky 
yers and calcareous clays. It presents exactly the same lithologic 
id paleontologic characters in the middle Rio Grande region that it 
>es in the Colorado River region. A microscopic examination of a 
>ecimen of the chalk collected 15 miles from Del Rio, on the road to 
agle Pass, showed its foraminiferal nature; Globigerina, Textularia, 
id Orbulina were present in very great numbers. 
!The first exposure was seen about 15 miles from Del Rio, on the 
tad to Eagle Pass. Other exposures were seen as far as Tulio Creek 
lias Moras Creek), about 33 miles from Del Rio. Pinto, Cow, and 
ilio (Las Moras) creeks flow over the chalk where the Eagle Pass- 
3l Rio road crosses the streams. On the road from Brackett to Del 
o exposures were seen as far as the first crossing over the Southern 
.ciric Railroad. 
At the crossing over Cow Creek there is an excellent exposure in a 
I iff, about 25 feet high, composed of layers of chalk, 1 foot or more 
i thickness, alternating with beds of yellow clay. From this place 
: i following fossils were obtained (locality No. 271): 
Cidaris ? s'p. , a detached plate. 
Gryphsea aueella Roemer. 
:.T. Durable: Bull. Geol. Soc. America, Vol. Ill, 1892, p. 221. 
>p. cit, p. 229. 
>unible lias used the name " Pinto" for these beds in this region (Bull. Geol. Soc. America, Vol. Ill, 
p. 222), but, as is here shown, there is no occasion for applying a new designation to them. 
