190 SUPPLEMENT TO THE CRAG MOLLUSCA. 
CONCLUDING REMARKS. 
Tux science of Palaontology being one of pure observation, the lapse of a few years 
may be expected to make considerable alteration in determinations previously arrived at ; 
thus, since the publication of the ‘Crag Mollusca’ I have been enabled to identify with 
existing species some of those forms which were considered to be extinct, and to correct 
errors consequent upon the possession, at the time, of imperfect specimens only, as well as 
those which the progress of our knowledge of the recent Marine Fauna had served to dispel. 
The ‘ History of the British Mollusca, by Messrs. Forbes and Hanley, having been 
published since the completion of my work, has furnished much information, and has 
supplied many notes for correction, which it had been my intention for some years past 
to publish with illustrations of new species obtamed. I have also had, since then, the 
still greater benefit of the ‘ British Conchology,’ by J. Gwyn Jeffreys, Esq., F.R.S. 
The Crag formations have of late much occupied the attention of geologists and 
paleontologists, and Mr. Prestwich, in the ‘ Journal of the Geological Society,’ vol. xxvui, 
1871, has published three papers upon the Crag, in which he has availed himself of the 
assistance of Mr. Jeffreys to furnish tabular lists of the Mollusca of the Coralline, and 
of the Red and Fluvio-marine Crags, and Chillesford bed. As the determinations arrived 
at by the last-named gentleman differ im so many instances from my own, I have not 
considered it necessary to review them all in detail, but at the end of this Supplement I 
have given lists of all the Mollusca which have come under my observation from the Upper 
Tertiaries of that part of England to which I have confined this Supplement, in the way 
they appear to me to be specifically separated. Several species were spoken of in my 
original work as having been obtained by myself in abundance, or, at least, as not at that 
time being difficult to find, and I fear that this statement may have given disappomtment 
to many collectors. Several species formerly abundant have, I am sorry to say, entirely 
eluded my search of late years, and this within a few yards distance of, and on the same 
1 The name “‘Coralline Crag” has been employed by myself for the older bed of these different 
formations, not only from what I conceive to be its special claim in regard to priority of date, but also from 
its correct and appropriate appellation. This name was given to it by Mr. Charlesworth, in 1835, in 
consequence of its composition being largely made up of what had been “‘Corallines,’’ or “little corals,” 
organisms so called by Ellis and others, such as Cellepores, Retepores, Tubulipores, Flustre, &e. &c., but 
which have since been separated from the true corals. The Red Crag, from its rusty or reddish-brown colour. 
