Jura Neocomian and Chalk of Arkansas. — Marcou. 35? 
that their statements be taken for exactly what they are. If 
correction is to be made, it is apparent that the sooner it is 
done the better it will be for the science both at home and 
abroad. 
How this correction will aflect two other terms, the Taconic 
and the Lower Cambrian., it is not my intention to inquire 
fully at this time. I would only call attention to the nearly, 
if not quite, parallel and almost identical lines of thought that 
prompted these other, and earlier, geological terms, and the 
great approximation they show to identity of stratigraphic po- 
sition. 
JURA, NEOCOMIAN AND CHALK OF ARKANSAS. 
.TuLES Marcou. 
The second volume of the Aiinual Report of the Geological 
Survey of Arkansas j for 1888 , issued August last is one of the 
most important contributions yet made to the geology of the 
country southwest of the Mississippi river. The title is : "The 
Neozoic geology of southwestern Arkansas," by Robert T. 
Hill, assistant geologist. On the back of the volume the title is 
only "Mesozoic." I shall confine my remarks to the Mesozoic 
series, which is the most valuable part of the work, passing 
over the first six chapters, on the geography, topography, 
Post-Tertiary and Tertiary formations. It is not because the 
first part of the volume is not worthy of consideration ; on the 
contrary, like the rest, it is a remarkable and well digested 
work, worthy of being reviewed by a specialist, who can better 
render justice and appreciate the stratigraphy of the Cainozoic 
than myself. 
The lower Cretaceous, or Comanche series, is composed of 
three groups. The lowest is the "Trinity division." Although 
professor Hill has spoken, in several of his papers on the 
geology of Texas, of that group under the names of "Dinosaur 
sand," 1887 ; "Basal sand," 1887 ; "Trinity beds," April, 1889; 
and "Trinity basal littoral beds," May, 1889 ; he had not given 
a true description before publishing his report of southwestern 
Arkansas. He even hesitated before placing it in the Creta- 
ceous system. In his first paper of April, 1887, he put it out- 
side of the lower Cretaceous — a true and excellent classifica- 
tion; then he enclosed it in his Comanche series, saying, 
