Mineralogy and Geology. 267 
g 
and, as seems to us highly probable from a careful consideration of the 
geological structure of the region, previous to the glacial epoch of the 
Sierra, and also previous to the erosion of the cafions of the present 
rivers, No pains will be spared, however, to investigate all the condi- 
tions of the occurrence of this skull, and they will be fully reported on 
at a future time. 
cia of bone wedged in the cavity. This she h : 
according to Dr. Cooper, a species now living in the region where the 
. skull was obtained. Although not competent to express a nion 
older than the Carboniferous or Devouian, in the mountain ranges near 
Austin. This expectation has been realized, and we are now in posses- 
Sion of a very interesting collection of fossils, obtained by Mr. A. Blateh- 
ley, in the vicinity of the Hot Creek Mining District, about one hundred 
miles southeast of Austin. This collection enables us to state positivel: 
that both Upper and Lower Silurian rocks occur in that district, and 
that they are well filled with fossils; not less so, indeed, to pene 
the specimens received, than the strata of the same age in New York, 
Ohio, Iowa, and Wisconsin, which they paanile in a most marked de- 
Sree, both lithologically and paleontologically. saeleaion 
The fossils “Sige the Hot tie district are mostly weathered out on 
the surfaces of thin slabs of bluish-gray argillaceous limestones, and are 
