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SUPPLEMENT TO THE CRAG MOLLUSCA. 



work, of comparing all the specimens and of giving them deliberate examination. The 

 Bridlington species have been examined by me either in the collection of Mr. Bean, now 

 in the British Museum, or by means of specimens kindly supplied me for the purpose by 

 Mr. Leckenby, to whom rny best thanks are due for his obliging readiness at all times to 

 assist me with specimens. The Burgh, Horstead, and Coltishall specimens, and those from 

 the Lower and Middle Glacial deposits, have all been sifted out by my son under my own 

 eyes from material obtained from time to time from the various localities by Mr. Hamier, 

 and most carefully guarded against intermixture or the possibility of the intrusion of any 

 other material or of specimens from any other place. The March and Hunstanton speci- 

 mens have all been examined by me in collections made by Mr. Harmer from those places, 

 and the Nar Valley specimens in the collection of the late Mr. Hose. The Ivelsea Hill 

 species are principally given on the authority of Mr. J. Gwyn Jeffreys, my son's collection 

 from that place comprising only a portion of the species enumerated by that gentleman. My 

 best thanks are due to Mr. Dowson and Mr. W. Crowfoot for the opportunity of examining 

 the Aldeby specimens, to Mr. Cavell for the sight of specimens from the Cor. Crag near 

 Orford, from Thorpe by Aldborough, and from Easton Cliff, and to Mr. Reeve for 

 specimens from Bramerton. Especially to Messrs. Alfred and Robert Bell for the use 

 of numerous specimens, and to the Rev. H. Canham, of Waldringfield, for his un- 

 wearied researches in both the Red and Coralline Crags, are my thanks due. I am 

 also obliged to Dr. Reed, of York, for the use of many specimens which he possesses 

 from the different Crags of Suffolk, as well as to Mr. E. Charlesworth, who has throughout 

 his life taken so active a part in the elucidation of the natural history of the Crags. I 

 must also express my thanks to Mr. Jeffreys for his readiness at all times to assist 

 me with the loan of recent shells in his possession for the purpose of comparison. I 

 have also had the assistance of my son throughout the preparation of this Supplement, 

 and in the re-examination and revision to which I have subjected the determination of 

 all the species given in the ' Crag Mollusca.' Tn all the instances where not otherwise 

 specified in the text the specimens are from my own collection, and of my own finding. 



In conclusion, I would add that I have studiously abstained from recognising the terms 

 " Quaternary " or " Post-Tertiary." Of the terms " Primary/' " Secondary," and 

 " Tertiary," adopted by early geologists for great geological divisions, the first has become 

 wholly obsolete. The term " Secondary " becomes yearly more and more vague, and less 

 and less used to define any natural division of geological time ; while the term "Tertiary" 

 alone remains convenient in consequence of the yet unbridged chasm which separates the 

 beds of that division from the Cretaceous group. To introduce, however, into geology 

 another division as {! Quaternary" or "Post-Tertiary " is not merely to import a term as 

 unmeaning as that of "Primary," which has been universally dropped, but one whose 

 limits cannot be defined by any constant feature, either in physical geology or in 

 paleontology; and it finds a foil when some of our leading naturalists insist, as 

 they have been lately doing, that Ave are still in the Cretaceous period. If we 



