108 rROF. J. PKESTWICE ON THE RELATION OF THE 



The freshwater shells in beds i to 7c consist of : — 



Anodonta cygnea, L. 

 Pisidiam amnicum, Miill. 

 Sphaeriura corneum, L. 

 rivicola. Lea. 



Bythinia tentaculata, L. 

 Paludina gibba, Sandb. ? 

 Valvata piscinalis, Mull. 



Bed g contains fewer species ; the chief are : — 



Planorbis complanatus, L. I Suceinea putris, L. 

 Sph^rium corneum, L. \ oblonga, JDrap. 



Beds e and /represent Mr. Reid's Arctic freshwater beds, in which 

 he has found, in places, Salix 2^olaris, Betula nana, and Hippuris 

 vulga7'is, with remains of Spermophilus ; while bed i is on the 

 horizon of his Leda-myaUs bed *. The lower beds would, I presume, 

 be included by Mr. Eeid in his Upper Freshwater and Forest-Bed 

 division. The relation to the lower and the Weybourn beds cannot 

 be seen in this part of rhe coast-section. 



The divisions of the strata under the Cromer Till (Lower 

 Boulder-clay) on the JSTorfolk coast, according to Mr. C. Eeid, 

 are : — 



Older Pleistocene / Cromer Till. 



(Glacial) \ Arctic Freshwater Beds. 



( Lecla-viyalis Bed. 



{Upper Freshwater Bed. 

 " Forest Bed " (Estuarine). 

 Lower Freshwater Bed. 

 (Wevbourn Crag. 

 Chillesford Clay? 



The minor subdivisions are subject to considerable variations, and 

 are of very restricted range, depending upon local conditions. It 

 seems to me that all the beds e to m (fig. 7) are members of one 

 series, and I have therefore grouped all down to the Forest Bed under 

 the one term of " Mundesley Beds " ; and as I take these beds to be 

 on the same horizon and synchronous with the marine "Westleton 

 Beds of Suifolk, the term "Westleton and Mundesley Beds " t will 

 serve to indicate the two tj^pes. 



Mr. Reid considers that these terms J can scarcely be adopted, 

 because the shingle " at Westleton is now believed to belong to 

 the Glacial Beds, and, at Mundesley, beds deposited under quite 

 different conditions, and showing marked changes of climate, are 

 included." It is quite true that the beds show somewhat different 

 conditions, but that arises solely from the emergence of this area, 

 and the introduction of a land- and marsh-fauna and flora oscillating 

 with a marine fauna as the sea from time to time encroached §. 



With respect to the climate, I do not see that the fossils indicate 

 anything more than the continuance of that lowering of temperature 

 which set in with the Crag beds. As the cold increased, many 



* Op. cit. pp. 37, 48, 83. 



t Eeport British At^sociation, 1881. X Op. elf. p. 9. 



§ Dr. Sandberger came independently to the same conclusion from an exami- 

 nation of the fossils. 



