153 
A 
SUPPLEMENTARY, 
OR STRATIGRAPHIC AL INDEX 
TO VOL. IV. 
Arranging ike Shells described therein , according to the, 
several Strata in which they were found imbedded , from 
the newest towards the oldest in the British Series. 
Howland Street, April 21 st, 1823. 
GENTLEMEN, 
ON presenting to you a continuation of those Stratigraphical Indexes to 
the Volumes of “ Mineral Conchology,” which I have been used to pre- 
pare for my highly valued and lamented Friend, your late Father, I 
cannot avoid expressing the great satisfaction I feel at seeing, how wel| 
the indefatigable and able Instructions of my departed Friend, and the 
large collection of Specimens and materials which he has left in your 
possession, is enabling you to continue, to support with credit and 
increasing usefulness, the important work in aid of British Geology, 
which Mr. Sowerby set on foot, more than ten years before his decease. 
In your youthful energy and love of the subject, and in the zeal and 
abilities of your many kind Contributors, I see with pleasure an assurance, 
that “ Mineral Conchology ; ” will continue its progress, until at length, it 
embraces every species of Shell, which can hi the meantime be found im- 
bedded, in each one oftlie Strata of Britain; — when this shall be accomplish- 
ed, and the rich stores of British Fossil Shells, thus classified, recorded and 
rendered comparable , shall have been compared by the Geologists of other 
countries, with the shells which the Strata thereof may entomb, then, I 
am of opinion, will Geological truth appear, and the last remains of 
visionary and wild Theories on the subject, entirely vanish ; by which 
Theories, until Mr. Smith (in 1792) commenced his practical investiga- 
tions, and mapping of the English Strata, the subject was obscured, and by 
which, unfortunately, many parts of it are yet disfigured, and the truths 
of nature concealed. 
As an instance,! will beg to advert here, to the manner in which Writers 
still cling to the unfounded dogma of an age gone by, which asserted, that 
“our coal-measures exhibit only fresh- water and land productions !” in 
despite of the evidence, which Shells recorded in your pages, of the 
several Genera Ammonites, Anomia, Cardita, Conularia,' Euomphalus , 
Lingula , Mytilus, Qrthocera, Pecten , and Terebralula furnish, to the con- 
trary of such assertion ; which I know 7 to be an unfounded one, from 
having seen fossil Shells, of probably four times as many Genera, esteemed 
marine ones, as are mentioned above, and very numerous Species of 
many of these, the individuals of which are innumerably scattered 
tb rough the coal series, in particular districts, in the east of Sutherland 
and of Dumfries Counties, in particular: anil believe that such shells 
are in few r Coal-districts wanting, if industriously sought after. 
More than four years ago, on considering the Maps by M. Ilalloy , and 
by Messrs. Cuvier and Brongniati, of the environs of Paris, it occurred to 
me, that the gypseous and other anomalous Strata, producing Bones of 
Quadrupeds, alleged fresh-water Shells, See. in the vicinity, and south- 
ward of Paris, are referable to unconformable patches of Strata , of a very 
modern era, compared with the strata analogous to the London Clay and 
Deep-Well series, and the upper and lower Chalk, all of whose southern 
edges these anomalous strata locally cover. On considering also, soon after- 
wards, the Map and Sections of the Isle of Wight by Mr. Webster, I 
clearly perceived there, the same unconformableness (and have often 
since mentioned the same to my Friends:) and so with regard to the 
patch of strata, since alleged to contain fresh water Shells, on and to 
t&e northward of Hord well -cliff. 
