7 4 * 
to each other, and the parts of the land above are level 
and alluvial, as if a lake had been there before the present 
chasm in the rock. On the southern rock (a dark grey 
limestone) these extraordinary split shells are found, and 
are situate about twenty feet above the level of the river. 
I am greatly obliged to T. A. Knight Esq., of Downton, 
for the first specimen of this shell in 1809; I have since 
received specimens from A. Carlisle, Esq., which have 
ranch assisted in illustrating its curious structure, collected 
by him when on a visit to the gentleman abovementioned. 
Arthur Aikin, Esq., had observed this formation and 
the dividing of the under shells, and mentioned them to 
me at a meeting of the Geological Society in February, 
1812, and Mr. Farey was so kind as to send me several 
specimens with the following interesting observations : 
u The divided shells which I sent to you were brought 
from Croft-Ambrey Park Limeworks, Herefordshire, about 
eight miles S.S.W. of Ludlow; the quarries are in a 
sudden valley \ m. N. of Croft Castle, where thirty feet 
thick of the rock is opened, a dim grey shattery Limestone 
with blue cores. A great many of the thin beds in this 
quarry abound with the divided shells in a very perfect 
state; and, with others, I also saw appearances of Entrochi 
and Coralloids in this rock, which here dips to the S.E. 
at the rate of about one in eight or ten, and it appeared to 
me to be the upper of the three Limestone rocks that I was 
hastily tracing in this neighbourhood in July, 1812, and 
to underlie a local patch of Clearhills coal measures, 
extending hence southward ; and though belonging to the 
same limestone rock as Tinker’s, Cairbarn, &c. hills to the 
N.E. and beyond the Teme, and in Hopton- Wafers, I do 
not find that they now join, but are separated by the wide 
excavated vale of the Teme, in the red marie and other 
under measures to this rock.” 
