WESTLETON BEDS TO THOSE OF XORFOLJC, ETC. 113 



§ 5. Conclusion. 



The plan I have therefore adopted has been to confine myself 

 to those localities where, owing to the Chillesford Clay or Forest 

 Beds intervening, there is no possibility of the Westleton Shingle 

 having come in contact with the Norwich Crag. Eor this purpose I 

 have limited the list of the marine MoUuscan fauna of the Westleton 

 and Mundesley beds (see p.ll5) to the species found at Eeydon, Easton 

 Bavant, Bacton, Mundesley, and West Eunton (the last two being in 

 the Leda-myalis Bed of Eeid). This gives a list of only 19 species, 

 all living, excepting possibly two, about which the most competent 

 authorities differ. Tellina obliqua was considered by Sowerby and 

 Searles Wood to be an extinct species, whereas by Forbes and Hanley 

 and Gwyn Jeffreys it was considered to be a variety of T. lata, a living 

 northern species ; according to Jeffreys Nucula Cobholdice is now repre- 

 sented in the seas of Japan by a variety of the same species ; whilst 

 Searles Wood considered that they are distinct and that the Crag 

 species is an extinct form. With two exceptions all the others are 

 existing British species, although on the whole they are of northern 

 types — 10 ranging to Scandinavia and 9 to the Arctic seas : Astarte 

 horealis is Scandinavian and Arctic only. The elimination of the 

 more southern types seems to constitute the distinctive feature of 

 this fauna. 



The land- and freshwater Mollusca, of which there are 53 species, 

 are from the freshwater beds {g to m, fig. 7) of the Mundesley 

 series — the Upper Freshwater and Leda-myalis Beds of Mr. Eeid. 

 They are, with three questionable exceptions, all living species. 

 All the others except four are species still living in Britain, but 

 having a very ubiquitous range from north to south. Of the four 

 latter, Valvata fluviatilis is now living in Belgium and Germany ; 

 Hydrohia Steinii in the north of Europe ; H. marc/inata in the 

 South of France ; while Corbicula fluminalis ranges from Thibet to 

 the Nile. The three extinct species include a slug (Lima.v modio- 

 liformis) ; Paludina gibha, formerly referred to P. contecta, a British 

 and Finnish species * ; and Hydrobia runtoniana : they are found 

 fossil also in North Germany. 



The freshwater bed {j) at West Eunton is rich in Fish-remains. 

 There are 10 species, all still living in the rivers of this country. 



The Eeptiles (2) and Amphibia (4), found in the same bed are 

 also living British species. 



Of the 21 species of Mammalia, 6 are extinct ; and it is to be 

 remarked that out of the total number there are 14 which are 

 not met with in the Forest Bed and make their first appearance in 

 this stage, and it is the same with all the Eeptiles and Amphibians. 



The 24 Plants are of special interest from the rarity of plant- 

 remains in such deposits. They are all living species, — 19 still 

 living in this country, 5 being now relegated to more northern lati- 

 tudes, and, as in the case of the Mammalia, a large proportion (14) 

 are confined to the Mundesley freshwater beds, though this may 



* P. glacialis and P. media are doubtful, and thought by Mr. Reid to be 

 derived. 



Q. J. G. S. No. 181. 1 



