Stratigraphy of Appalachian Vlrgmia. — Darton. 13 
following list in which are classified the strata from Silurian to 
Lower Carboniferous : 
Names adopted by 
Rogers' 
Other names which 
Tliickness. 
(Tl'Oup. 
U. S. Geol. Survey. 
number. 
have been used. 
1 Greenbrier limestone 
XI 
Carboniferous. 
i (W. B. Rogers.) 
Pocono sandstone 
X 
Montgomery grits 
(W. B. Rogers.) 
GOO to 800 ft. 
1 (2dGeol.Surv.of Pa.) 
\ Hampshire formati'n 
IX in part. 
Catskill (in part?) 
1000to;400ft. 
Devonian . 
- Jennings formation 
VIII " 
Chemung " " 
2800 to 3200 ft. 
f Romney shales 
VIII " 
Hamilton " " 
500 to 900 ft. 
1 Monterey sandstone 
VII 
Oriskany 
to aoo ft. 
Lewistown limestone 
VI 
Lower Helderberg 
300 to 600 ft. 
1 (2d Geol. Surv. of Pa.) 
Silurian. 
1 Massanuttensandst'n 
IV and V 
Medina and Clinton 
600 to 800 ft. 
Martinsburg shales 
III 
Hudson River 
SOOtoHfiOft. 
1 Shenandoah lime- 
II 
Valley limestones. 
1500 ft. 
!_ stone 
Trenton, Chazy. Levis, 
Calciferous.' 
The term "Shenandoah limestone" " is thought to be ver}- appro- 
priate, for the Shenandoah valley and river are well known 
features of its area. The formation comprises in the Staunton 
region a great mass of impure magnesian limestones below, grad- 
ing upwards through a series of cherty beds of no great thick- 
ness into several hundred feet of light-colored, heavily bedded, 
purer limestones. The lower beds were not found to be fossilifer- 
ous. In the cherty beds only a few middle Ordovician gasteropods 
were found. In these beds the distribution of cherts is irregular 
in amount, horizon and continuity. The upper member is spar- 
ingly fossiliferous at many localities with a middle to upper 
Ordovician fauna in which the forms Ort/a's occidcntdlis^ 0. 
testudinaria. Leptania aJtcnt<(t((. 'M\d Cltatetcs lycoperilou were pre- 
dominant. Phurotomaria >>ubconica, Conularia trfntonensis. 
Flafijnotiis trcntonensis and several others were also noted. 
In his reports and notes Kogers made no attempt to su1)divide 
the great limestone series but fully recognized the charactertistics 
of its several members. In his contributions to Macfarlane's 
Guide the upper beds are placed in the "Trenton," and this desig- 
nation has been generally applied to them. J. L. Campbell, in 
the paper above referred to, describes five subdivisions in the 
Lexington region, but in the Staunton region no lines of separation 
were found to be sufficient for areal distinction. 
The Martinsburg sliales succeed the Shenandoah limestoiu' witli 
a thin series of alternating: tliiii l>edded limestones and slates at 
