A SUPPLEMENTARY INDEX TO VOL. L 
Arranging the Shells described therein accord - 
ing to the several Strata in which they are 
found imbedded , from the newest towards 
the oldest in the British Series . 
The completion of my first volume of Mineral Conch- 
ology, the publication of Mr. William Smith's very long 
expected Map of the Strata of England, Wales, &c» 
and its accompanying Memoir, and the publication of Mr. 
Aaron Arrowsmith s very large and minutely detailed Map 
of England and Wales, having all happened about the same 
time, have given the means and increased the facility of ar- 
ranging the 212 species of Shells contained in the preceding 
Index, according to their respective places in the Series of 
strata; that is, according to the eras in which these shell-fish 
respectively lived, beginning with the most recent. 
For this Supplementary Index I am indebted to my inde- 
fatigable friend, Mr. John Farcy sen. author of the Mine- 
ral Report on Derbyshire, and many geological papers in 
the Philosophical Magazine , &c., who desires it may not 
be received as a perfectly correct arrangement, for which 
the localities mentioned were not always sufficiently minute 
and particular, nor is the order of the strata in every in- 
stance settled beyond controversy, but is submitted for the 
revisal and free correction of my readers and correspondents, 
x either in their letters to me, or to Mr. Til loch, the Editor 
of the Philosophical Magazine ; in which useful work Mr. 
F. proposes to publish an Alphabetical List of all the places 
herein mentioned, with their situations and strata , and a 
List of the genera and species of Shells found in each place; 
referring to the tab. and fig. in my plates wherein they have 
been delineated. 
I will take this opportunity of requesting the increased 
attention of all the kind correspondents and contributors of 
Shells for this W ork, to the giving of the name and precise 
situation of the place (by bearings and distances from one or 
more adjacent towns) whence their specimens were taken, 
that have already, or may hereafter be sent to me, and the 
kind of stratum in which they were imbedded : and from 
such as are possessed of Mr. Smith’s Map, I should be glad 
to receive the mention of the name of the stratum to which 
each Shell belongs, that I maybe enabled to publish the 
same with its description, and to mention its cotemporary 
Shells in my future numbers. 
