188 SILURIAN. 
LupLow BoNE-BED AND DOWNTON SANDSTONE. 
The Bone-bed, indicating a long period of rest, covers the sandy Upper Ludlow rocks over a large area. 
At Ludlow it is divided into two thin bands not an inch thick. At Norton, near Onibury, it is a foot thick, 
one mass of fish defences (Onchus), shagreen of some shark-like or Acanthodian species, and shells of Brachio- 
poda—Discina and Lingula—with a few Pteraspid fish. The whole appearance is that of a drift in shallow but 
quiet water, and the fact that the Bone-bed is everywhere covered by the Downton Sandstone rock shows that 
the deep-sea condition had passed, and the coast-line raised. West of the central Silurian region the Bone-bed 
is not known; but within that region it ranges from Ludlow to Malvern, thence to Woolhope and Hagley ; but 
fails at Usk, though the fish defences and bones of the same species are found in Red Downton rock of 
coarse texture. 
The Downton Sandstone is the true top of the Silurian system, and contains several Ludlow shells. Over 
this, the red sediments, evidently accumulated in land-locked seas and estuaries, contain abundance of Pte- 
raspid and Cephalaspid fish; and only a single shell, Lingula cornea, and a few crustacea, Pterygotus Banksw 
and Beyrichia, rise into the base of the Old Red Sandstone (Ledbury Shales). 

(Note. The term Tilestones is technically applied to the flaggy- beds at the top of the Ludlow series of rocks.) 




Case and : Moa(ne) 
Column of et renee © ESO Names and References; Observations, &c. Numbers and Localities. 
Drawers. - Synopsis: and Figures of Genera. 
Ggd A good slab of the Micaceous Tile- | b. 121, Storm Hill, Llan- 
stones. deilo. 
[Plant fragments, probably of low Ly- | Hagley, Ludlow, &c. 
copodiacew, are very common in the 
Silurian district. There are but 
few in the collection. ] 
Pachytheca spherica, Hooker (Silu- | Woolhope. 
ria, 3rd ed. pl. 35, fig. 30. Hooker, 
Quart. Journ. Geol. Soc. Vol. XVII 
p- 162). This very common seed- 
case or spore of (probably) a water- 
plant abounds in Downton Sand- 
stone. 

Actinophyllum or Spongarium? or | Ludlow. 
some allied plant half an inch in 
diameter, is frequent near Ludlow. 

CRUSTACEA (Merostomata, Dana). 
Pterygotus problematicus, Ag., 6 ft. Ludlow. 
long. 



