Chap. VI.] 
LOW EE WENLOCK FOSSILS. 
Ill 
It is on the outside of the inner dome of these symmetrical elevations 
that the Lower Wenlock zone, as above shown, is most clearly exposed. 
Having been raised equably on the outward face of the dome of Haugh 
Wood, the nature of the calcareous deposit can be seen in detail on the 
sides of the roads, whilst the best limestones, which have been largely 
opened out since I described the tract, afford numerous fossils unknown 
when the ' Silurian System ' was published. 
In ascending order, the beds may be thus described. The top of the central 
dome of Woolhope, c, with its transition beds, is a greenish, earthy, calcareous 
sandstone, containing the following fossils, as described in the last chapter on the 
Llandovery rocks : — Pentamerus lens, Atrypa reticularis, Petraia bina. This 
course is followed by shale with calcareous gritty flagstones, containing the large 
Pentamerus liratus, Foss. 15. f. 3 (p. 90), and in the more nodular portions abun- 
dance of Leptsena transversalis and Atrypa reticularis. Layers of an impure 
earthy limestone succeed, containing Strophomena depressa, a species which, 
though occurring in the Lower Silurian rocks of North Wales, becomes much 
more abundant in the Wenlock formation. 
In the next overlying bands of shale, we pass fairly into unequivocal Upper 
Silurian. In these, calcareous matter so increases as to form strong beds of dark 
indigo-coloured, argillaceous limestone, which is characterized by cross veins of 
pink and white calcareous spar. The strongest bed (about 10 feet thick) is a 
tough, impure, earthy limestone, largely extracted for the roads ; and it is again 
covered by a stratum of purer limestone, followed by shale with an upper bastard 
limestone. Now, although the whole of the calcareous courses of this subfor- 
mation have no greater maximum thickness than from 30 to 40 feet, still the rock, 
together with its interpolated beds of sandy shale, is seen to occupy a very great 
surface on the annexed Map, from its being so equably spread out at a low angle 
of inclination. Among the chief fossils of this limestone, which I have collected 
on the spot, are the two Trilobites of the following woodcut, viz. Bumastus Bar- 
riensis, Foss. 17. f. 2, and Homalonotus delphinocephalus, f. 1. There are also 
Phacops caudatus, Cornulites serpularius, Orthoceras annulatum, a species of 
Phragmoceras, Euomphalus sculptus, Spirifer elevatus, Strophomena imbrex, S. 
pecten, S. depressa, Leptaena transversalis, Orbiculoidea Forbesi, Atrypa reticu- 
laris, Rhynchonella Wilsoni &c, and rarely Orthis elegantula. 
Fossils (17). Trilobites of Lower Wenlock or Woolhope Limestone. 
Here again, as in Radnorshire, we have a great predominance of true 
2. Bumastus Barriensis, 
and profile of the head. 
1. Homalonotus delphi- 
nocephalus, Green. 
These figures are about 
one -third the natural size. 
