Strati gri(2>hy of A/qxiIacJiian Yirginla. — Dartort. 17 
of the ores and the impregnation of the surrounding rocks with 
more or less ferruginous material. 
The Devonian formations in central Appalachian Virginia com- 
prise from 5,000 to G,000 feet of arenaceous and argillaceous 
deposits, separable into three series. The basal members are 
fissile shales, in greater part black or dark brown in color, con- 
taining occasional thin beds of sandstone and limestone. Their 
average thickness is about GOO feet. They give place to a series 
of light colored shales, in which olive, grey, and buff tints pre- 
vail, with interbedded light colored sandstones, averaging in all 
about 3,000 feet in thickness. The local sequence of beds in 
this series is variable, but the medial portion consists largely of 
arenaceous members. The upper series is characterized by thin 
bedded, relatively hard, more or less micaceous sandstones with 
shale intercalations, in greater part dull red, dark grey, and 
brown in color. Its average thickness is about 1,200 feet. 
These series intergrade through beds of passage often amount- 
ing to several hundred feet in thickness, but this amount is vari- 
able in different parts of the region. In his reports and notes 
Rogers classes the two lower series under his No. VIII, and sepa- 
rates the upper member, possibly more, as No. IX. The three 
series have also been more or less generally known as Hamilton, 
Chemung and Catskill, but without any definition of their range. 
Notwithstanding the extensive intergrading, the series are so well 
characterized as wholes that it seemed best to separate them as 
formations. As in the case with most of the other formations, 
it was found that there were no names in existence which could 
be employed with any degree of definiteness, so new names were 
selected. The names adopted were Romney shales, from Rom- 
ney in West Virginia, for the basal series of dark shales, Jen- 
nings formation, from Jennings' gap and Jennings' branch in 
western Augusta county, Virginia, for the medial series of light 
colored shales and sandstones; and Hampshire formation from 
Hampshire county. West Virginia, for the uppermost series of 
dark sandstones. The Devonian formations are not fossiliferous 
at many horizons in the region west of Staunton. In the Rom- 
ne}^ shales the following species are Corniferous: Discinu hnhmsis, 
D. inini(t<i,Orflns /eacosiri, StropJiodontd demissd, Cyrtlna luimil- 
tonensi-s, Splri/crd mHcronattis, S, granulifera. and LeiurhijnchuH 
limitaris. This is a Hamilton group fauna, but the stratigraphic 
