xl DESCRIPTIVE REMARKS. 
Fossits or THE WENLOCK Rocks.* 
The Upper Silurian rocks are arranged by Sir R. Murchison into 
two groups—a Lower or Wenlock, and an Upper or Ludlow group. 
The lower division includes the Tarannon and Denbighshire slates, the 
Woolhope shale and limestone, and the Wenlock shale and limestone. 
Tarannon Sates and DENBIGHSHIRE SANDSTONES, SHALES, and 
States.—These are local formations, occupying an intermediate position 
between the Llandovery rocks and the true Upper Silurian. The 
Tarannon shales at Tarannon, in Montgomeryshire, form a band of 
great persistence and considerable thickness, extending from Llando- 
very and Montgomery into North Wales. In these deposits fossils are 
rare, and not sufficiently characteristic to determine with certainty 
whether these strata should be classed with the Upper Llandovery 
rocks or those of the Wenlock formation. The Denbighshire sandstones, 
&c., rest conformably upon the Tarannon slates in the same counties of 
Radnor and Montgomery, and in North Wales; the fossils in the 
Denbighshire flags being unquestionably of the Wenlock type. 
The Lower Wentock or Wooxnop:e series of strata derives its name 
from its occurrence at Woolhope, near Hereford, where it is superim- 
posed upon the Upper Llandovery formation; the same general order 
of succession is also exhibited in the Malverns, May, and Huntley 
Hills, Gloucestershire. The Wenlock shale is of considerable thick- 
ness, and occurs both below and above the Woolhope or lower limestone ; 
in the Malvern and Woolhope districts it is occasionally very fossilife- 
rous. In some parts of Wales it occurs as shale, but in Denbighshire 
it is represented by hard, slaty sandstones and schists. The Wenlock 
limestone, or upper member of the group, is usually of a lighter grey 
colour than the lower or Woolhope. In the districts of Malvern, 
Woolhope, May Hill, and Usk, as well as in Shropshire, it is largely de- 
veloped; though very thick near Wenlock, it thins out rapidly to the 
south-west. 
In the north-western part of England, especially in the counties of 
Westmoreland and Cumberland, and the adjacent tracts of Lancashire 
and Yorkshire, the Silurian rocks are extensively developed; towards 
the south and south-east, the Lower Silurian strata are succeeded by 
newer deposits, which, although of very different mineral characters, 
clearly represent, by position and fossils, the Wenlock and Ludlow 
formations. 
Silurian rocks, particularly those belonging to the lower division, 
are spread over a very large area in the south of Scotland; whilst in 
*In the Table of Fossiliferous Strata (ante, p. viii.), the Upper Llandovery 
Beds or May Hill Sandstone is included with the Upper Silurian Rocks, as forming 
its natural base. 
