Mineralogy and Geology. 269 
On the Mexican Boundary Survey, a few fragments of fossils were 
found in the superficial detritus, near El Paso (longitude 106°), which 
indicated the existence of Silurian rocks in that vicinity; but none ap- 
pear to have been found in place. Professor Hall remarks that “the 
the Carboniferous, this reference can only be taken as expressing a con- 
. 
remarkable fact that these rocks have not been di : 
mountains; and should farther explorations fail to reveal their presence, 
-it will throw a new light on the history of the physical development of 
the central and western portions of this continent. Taking into view 
what has now been communicated, and what was stated in my previous 
Among the specimens collected by Mr. Blatchley, as also by Mr. Clay- 
ton, Mr. Melville Attwood, and Dr. ©. L. Anderson, and now at our office, 
there is a considerable number which demonstrate or existence of an ex- 
from each other. recent 
than the Jurassic, in Nevada, has not yet been proved ; but, as Mr. Gabb 
at the hands of Messrs, Meek and Gabb, or other competent 
gists; and we expect that our.collections from that state will be largely 
increased during the present year.—Proc. California Acad. Nat. Sc., 
Ni, 307, : 
4m. Jour. Sc1.—Szcoxp Series, Vou. XLII, No. 128.—Manca, 1867. 
35 
