676 



EEPO.HT — 1895. 



with some thousands of specimens of Southern MoUusca for every boreal shell we 

 could discover. Among the extinct g-enera. a study of the more abundant forms 

 also shows an equal preponderance of Southern types. Only one specimen of a 

 truly Arctic shell, viz., Cerithiopais lactea, has been met with in the Coralline Crag, 

 but as to its correct identification Mr. Wood had considerable doubt. 



Professor Prestwich, on the contrary, believes that ice action had come into 

 existence even at the commencement of the Coralline Crag era, resting his opinion 

 on the occurrence of a block of porphyry in the basement bed at Sutton, which, 

 however, was neither angular nor striated, but which he thinks could only have 

 been transported either from Scandinavia or the Ardennes by floating ice. No 

 ice, however, reaches our shores at the present day either from Belgium or Norway, 

 and the winter climate of Northern Europe would have to fall considerably before 

 this could take place. At present there is a difference of not less than 10° Fabr. 

 between the temperature, both of the sea and the atmosphere, in the British and 

 Mediterranean areas. 



Summary of the abundant and characteristic species of MoUusca 

 occurring i^i the Coralline Crarj. 



Not known as living (37 per cent.) 

 Living in distant seas : — 



Pacific 



Atlantic . 



West Indian . 



Sovith African 



North American 



89 



Living in the Mediterranean . . . .13.3 

 ,, not in the Mediterranean but in the 



West European area .... 9 



Not known to ranee to the South of British seas 



142 

 1 



240 



Species of European MoUusca occurring abundantly in the 

 Coralline Crag. 



Southern and not British (28 per cent.) 42 



British (rare) and Southern 9 



(35 per cent.) 

 British (characteristic) and Southern 

 British and not Southern . 



.'-.1 



91 



1 



143 



2. On the Derivative Shells of the Bed Crag} By F. W. Harmer, F.G.S. 



It has been generally held by geologists, among whom may be mentioned 

 Mr. Searles V. Wood, Professor Prestwich, Sir Charles Lyell, and Mr. Charles- 

 worth, that a considerable number of the MoUusca found in the Red Crag are 

 extraneous. Mr. Wood, in the supplement to his well-known Monograph, 

 expresses the opinion that 118 species have been derived from older deposits, 

 principally from the Coralline Crag. Professor Prestwich thinks that only 46 

 species are derivative, but his list contains 13 which Mr. "Wood, on the contrary, 

 believes are Red Crag forms. 



There seems much, a priori, to support the ^derivative theory. The great 

 denudation to which the Coralline Crag has been exposed by the Red Crag sea; 



' This and the previous paper will be published in the Geol. Mag 



