410 F. W. Harmer — Position of the Coralline Crag. 



the following classificatioa of the various divisions of the Anglo- 

 Belgian deposits, to which, with the exception of the point alluded 

 to above, I still adhere: — 



Upper Pliocene. 

 Belgium and Solland. England. 



Amstelien. Butleyan and Newbournian. 



Poederlien » W U ' ^ Walton horizon. 



Scaldisien \ ^ onian. j Oakley horizon. 



Casterlien (zone k Isocardia cor). Coralline Crag. 



Lower Pliocene. 

 Diestien (zone a Terehratala grandis). Lenham Bed. 



In his sj-noptical list of 1874^ Wood reported 430 species of 

 Mollusca as known to him from the Coralline Crag; of these only 

 about 90 had been found at that time at Walton, but even then 

 he had come to the conclusion that there was a close connexion 

 between the two deposits and that his original reference of the 

 former to the Miocene had been a mistake. 



The investigations of Professor Kendall and the late R. G. Bell at 

 Walton and ray own at Little Oakley have strongly supported 

 Wood's later opinion. Of the 430 Coralline Crag species referred to, 

 about 270 are now known from the Waltonian or some later horizon, 

 "while hardly auy of the remainder can be considered common or 

 representative Coralline Crag forms. To regard a species of which 

 only one or at the most a very few specimens have been obtained 

 during 'the labours of a century as of equivalent value, for purposes 

 of analysis, to others of which a large number could be found at any 

 time in a few days, is misleading. It is by the general facias of 

 a fauna — by the abundant and not by the rare examples — that we 

 should be guided. 



While, therefore, nearly all the characteristic Coralline Crag 

 species continued to exist in the Anglo-Belgian basin during 

 Waltonian times, or even to a later period, no such correspondence 

 can be traced between its fauna and that of the Belgian Miocene, 

 zones a Panopma Menardi and Pectunculus pilosus of Van den Broeck 

 (Anversien, Newton). Out of 230 species of moUusca reported 

 from the latter horizon by the former observer, only 106 are known 

 from the Coralline Crag, the rest being generally and distinctly of an 

 older type.^ 



The true Belgian equivalent of the Coralline Crag is the zone a 

 Isocardia cor, the fauna of the two being practically identical. Of 

 about 150 species given by M. Van der Broeck ' or M. Bernays * from 

 the latter (for which I have revived the name of Casterlien), all but 

 about half a dozen have been obtained from the Coralline or the 

 Waltonian Crags. The Casterlien, moreover, bears a relation to the 



1 Men. Crag Moll., 1st Suppl., pt. ii, p. 203, 1874. 



2 Ann. See. malac. Belg., vol. ix, pp. 118, 134, 1874. 



* Op. cit., p. 187; Bull. See. Beige Gf^ol., vol. vi (Mem., pp. 120, 130, 

 1892). 



■* Bull. Soc. Beige Geol., vol. x (Mem., p. 128, 1896). 



