J. P. Kimball on the Geology of Chihuahua. 387 
the significant evidence above brought forward to prove the 
Cretaceous age of the same limestone. In the geological sketch 
given by Dr. Wislizenus, the formations are laid down accord- 
ing to his description.* 
The number of Cretaceous fossils collected by pr west 
of Presidio del Norte, quite disproves the position of Dr. Parry, 
viz., that the “natural boundaries of this basin (near Presidio 
del Norte) consist of irregular mountain ranges composed. prin- 
cipally of carboniferous limestone similar to that seen above” 
(near El] Paso. But Dr. Parry in this matter seems to follow 
Prof..Hall who referred the limestone of this section to the car- 
of a simple specimen from the rapids of the Rio Grande, in 
which no fossils could be recognized.t With regard to the 
‘compact and vesicular layas, and volcanic and friable breccias, 
ete.,” thus termed by Prof. Hall, in the collection of Dr. 
it is proper to suggest the former to be referable to the cantera 
im some of its aspects of coloration, aggregation, and weathering, 
and the latter to be the cemented rubble above noticed. The 
limestone back of Presidio del Norte, unmistakably. Cretaceous, 
occurrence of Texas Cretaceous fauna 
were found by the late Mr. Rémond. Prof. Gabb, to whom -_— 
ed o s 
e an editorial critique on a geological map by Jules Marcou (this 
Journal, vol. xvii, p. 202), by him attributed to Prof. Hall (Geol. North America, 
two reports, etc., 1858, pp. 93 and 98.) 
can Bound. Surv., i, Pt. 2d, p. 50. 
