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and is usually divided into au upper series, under tlie name of 
‘ Wenlock limestone and shale/ and a lower by the name of 
‘Woolhope beds/ In North Wales the lower beds rest con- 
formably on the Denbighshire grit and flag series. The 
Woolhope limestone is supposed to be only locally developed. 
The fauna of the group consists mainly of Crinoids and Corals ; 
but Brachiopods occur also in great abundance, and nume- 
rous new species have been lately added to the fauna by the 
researches of Mr. Gr. Maw and Mr. Davidson. Mr. Maw esti- 
mates the thickness of the group in Shropshire at over 2500 
feet. As previously stated, I exclude the typical so-called 
Denbighshire grit and slate series from the group, believing 
that those beds are for the most part on a lower horizon than 
any rocks usually included in this group in Shropshire. 
Shale and Limestone. 
Shale, Limestone, and Flaggy Beds. 
Ludlow Group . — This group in Shropshire attains a thick- 
ness of from 1400 to 1800 feet. It consists mainly of dark 
grey argillaceous shales with calcareous concretions, and lime- 
stone. It is divisible, however, into two portions. The upper 
consisting of light- coloured grits and shales, and the lower of 
the ‘ Aymestry Limestone series/ The fauna of this group is 
important from its including the first indications of vertebrate 
life as fish remains. Until the discovery by me lately of the land- 
plant remains in the Denbighshire grit series ; it was also sup- 
posed that the first evidences of a terrestrial flora occurred in 
these rocks. The fauna of this group for the most part is 
highly Silurian in type, but the topmost beds appear lithologi- 
cally and paleontologically to be passage-beds connecting the 
Silurian and Devonian formations. 
Upper. 
Lower. 
Shales, Flaggy Sandstones, and Grits. 
Hard Flaggy Shales, with Bands of impure Limestone. 
