﻿CRETACEOUS BRACHIOPODA. 



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SUPPLEMENT TO THE BRITISH CRETACEOUS BRACHIOPODA. 



Eighteen years have elapsed since the publication of my ' Monograph of British 

 Cretaceous Brachiopoda.' The first part appeared in August, 1852 ; the second and 

 concluding part in May, 1855. 



In the mean time many geologists and palaeontologists have been hard at work in 

 this country and on the Continent, studying the stratigraphical succession of the 

 numerous deposits of which the Cretaceous System is composed, as well as the organic 

 remains they contain. A very large mass of additional and valuable information 

 has thus been gained to science since 1855 ; and this will necessitate some alterations 

 and considerable additions to the Monograph, which in 1855 had been made as complete 

 as it was then possible to make it with the information and material in our possession. 

 In the 'Geological Magazine,' vol. vi, 1869, I endeavoured to assemble and publish 

 the principal views entertained by foreign geologists with regard to the divisions of 

 the Cretaceous System ; and it will be there seen that, although they differ to some 

 extent with respect to the number of the divisions into which the " system 3> should 

 be separated, they are all very much of the same mind with reference to the order 

 of sequence generally. 



In no single locality can we expect to find the succession complete, or representing 

 all the local phases which certain divisions will assume in one or another locality ; so 

 that it is sometimes difficult to correlate the beds occurring in one country with those 

 found in another, and especially so for widely separated districts. 



Since my Monograph was published many geologists, — among whom we may name 

 Messrs. Hebert, Cornuel, Coquand, Lory, Tombeck, Pictet, Velain, De Loriol, Zittel, 

 Schloenbach, Strombeck, Giimbel, Credner, Geinitz, and others on the Continent, — 

 Messrs. Godwin- Austen, Judd, Topley, Meyer, Walker, Seeley, R. Tate, Caleb 

 Evans, Wiltshire, Morris, Etheridge, Whitaker, R. Lankester, M. Norman, and some 

 others in this country, have powerfully contributed towards the advancement of our 

 knowledge upon this subject ; but there remains still much to be done before geologists 

 will have become quite unanimous in their terminology or as to the number and value 

 of all the divisions they respectively propose. I will briefly point out some of the 

 improvements effected in the divisions of our British Cretaceous System, which affect, 

 to a great extent, the distribution and localisation of the species forming the subject 

 of this Monograph. 



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