VINE : PAL^OXTOLOGY OF THE WEDLOCK SHALES. 
231 
traca and Protozoa, have passed throiigli my hands, and have been 
named and compared with my own. 
" The Tickwood beds contain all the five species of Spirifer found 
in the Upper Silurians of Shropshire, with a larger proportion of 
individuals than in any other zone. The Tickwood beds are also the 
highest horizon in which the new genus Glassia occurs, and Orthis 
biloba here attains its highest limit, with the exception that a few 
individuals occur rarely in the Wenlock limestone and Lower Lud- 
low,* 
Below the Tickwood there is another series of beds which are 
sub-divided by Messrs. Davidson and Maw as follows : — 
Barren shales of Coalbrook Dale — 
Thickness. 
" Coalbrook Dale beds " 1100—1200 feet, 
Fossiliferous zone of Buildwas — 
" Buildwas beds " 80— 100 feet. 
Barren shales of Buildwas Park — 
" Basement beds " 500— 600 feet. 
" These soft shales have largely determined the configuration of 
the contours of the district, and represent the sweeping Ape Dale 
valley of denudation, which spreads out for twenty miles below the 
supporting ridge of Wenlock limestone of Wenlock Edge, and have 
in Coalbrook Dale yielded to the excavation of the picturesque 
valley." f 
No. 43 washing is from these middle shales, or Coalbrook Dale beds, 
and is derived from Marmwood, which is situated between 
Coalbrook Dale and Buildwas. 
Here the material is more water-worn than in any of the beds 
examined, at the same time much of the fauna is very characteristic, 
as will be noticed by a reference to the list. With regard to abund- 
ance of individuals this washing will vie vrith any of the other beds, 
but it appears to me that though the Coalbrook Dale beds may have 
a fauna of their own, still the persistent character of the fossils indi- 
cate a beach-like accumulation of deeper-sea forms. 
The Buildwas beds, certainly the most abounding in organic 
-♦-Davidson, Geol. Mag., 1881, p. 103. f Ibid, p. 104. 
