The Texas Cretaceous. — Marcou. 99 
taining a chapter "Gesteine cler Kreideformation," pp. 373- 
387, and a "Geognostische Karte von Texas 1 ' ; and in 1852 he 
completed his publication by the issue of a quarto volume, 
Die Kreidebildungen von Texas und ihre organischen Einsch- 
lilsse, Bonn. On page 25 of the last work he gives his conclu- 
sions and general section of the Cretaceous strata of Texas as 
follows: (1) The Cretaceous formation is composed exclu- 
sively of limestone. (2) In the plains at the foot of the 
Texas plateaus the Cretaceous strata are composed of white 
limestone, more or less marly, of small thickness; while on 
the plateaus the rocks are very thick, hard limestone, alter- 
nating with beds of silex and marls. (3) The Cretaceous of 
Texas belongs in totality to the deposits posterior to the 
Gault and corresponds to the White chalk (etage iSenonien, 
d'Orbigny) and the upper part of the Chloritic chalk (etage 
Turonien, d'Orbigny). 
Roemer does not seem to have seen anywhere the superpo- 
sition of his two groups of Cretaceous rocks, railed by him 
Cretaceous of the plains (the Cretaceous at foot of highlands, 
of Hill) and Cretaceous of tin- plateaus (Cretaceous of high- 
lands, of Hill), although he inclined toward the idea that tin- 
chalk of the plains is older than the chalk of the plateaus, a 
rather grave error. On his geological map Roemer colors, as 
Cretaceous, parts of Texas which do not contain Cretaceous 
rocks, but are covered by the Carboniferous, the Dyas, tin- 
Trias, and the Jura ; the three last great formations having 
entirely escaped his researches. 
In 1852, Dr. G. G. Shumard accompanied, as a surgeon and 
naturalist, ('apt. R. B. Marcy, in an "Exploration of the Red 
river of Louisiana." He repeated the conclusions of Roemer 
in regard the Cretaceous formation of Texas, referring it to 
tin- Etage Senonien d'Orbigny. 
In 1853, I explored the 35th parallel of latitude, with Lieut. 
A. W. Whipple's expedition, for a Pacific railroad survey. 
In my two reports, printed in L855, and dated .Inly and Sep 
tember L854, in House Documents 12'.). Washington. I recog 
ni/.ed tin- Neoeomian at Comet creek, Fort Washita, and on 
the Kim fork of tin- Trinity river, showing for the first time 
in North America the existence of tin- Lower Cretaceous as 
in Europe. I developed my observations and published -■ \ 
