INTHODUCTION. 



The best general account of the Chalk Formation of England will be found in the 

 ' Geology of England and Wales,' by Conybeare and PhilKps, 1822, in which is em- 

 bodied a detailed description of the Chalk Cliffs in the neighbourhood of Dover by 

 Mr. W. Phillips, published in the fifth volume of the * Transactions of the Geological 

 Society.' The divisions of the Formation which Mr. Phillips has pointed out, are more 

 minute than can be followed in the present Monograph, since few collectors attend to the 

 precise part of the series from which their specimens are derived. I have, therefore, 

 usually contented myself with referring specimens to one or other of the following great 

 divisions of the Chalk, which are easily recognised, although they are not separated by any 

 well-defined lines. 



1. Upper Chalk; my specimens of which are principally from Norfolk, or from 

 Gravesend and Northfieet : this division is rich in Organic Remains. 



2. Middle Chalk, which contains but few Fossils : those examined are mostly from 

 Kent, Surrey, Sussex, and the Isle of Wight. 



3. Lower or Grey Chalk, containing numerous Fossils, especially Ammonites and 

 Turrilites : the neighbourhood of Dover, and of Lewes, and the Isle of Wight furnish 

 large supplies ; many specimens have also been procured from the numerous Chalk-pits 

 along the foot of the North Downs, and others have been obligingly sent from Devizes, 

 by Mr. W. Cunnington. 



4. The " Chloritic Marl " of the Isle of Wight, a bed of some six or eight feet thick at 

 the base of the Chalk, is very rich in Organic Remains, with which I have been most 

 liberally supplied from the rich Collection of Mr. S. Saxby, Jun., of Bonchurch. The 

 " Chalk with Siliceous Grains," of Somersetshire, is probably on the same parallel as the 

 " Chloritic Marl," and also contains abundance of Shells, of which a large collection 

 formed at Chardstock has been. most obhgingly lent me by Mr. J. Wiest : these have the 

 advantage of being far better preserved than is usual with the Chalk Fossils. I have also 

 had the use of Collections from this bed, belonging to Mr. E. H. Bunbury and 

 Mr. Morris. 



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