392 PEARCE ANO MAYFIELD : MOLLUSCA OF EAST NORFOLK. 



further interest attaches to these valleys, inasmuch as within 

 the days of history they formed more or less arms of the sea. 



The other area is (2) the upland district of low undulating 

 hills which hardly rise higher than 100 feet above the sea. 

 These uplands are chiefly arable land, in a high state of cultiva- 

 tion, for the most part treeless, and geologically composed of 

 thick glacial beds of gravel, clay, and crag, resting upon the 

 white chalk, which is not often visible except in cuttings and 

 pits. These features sufficiently explain the molluscan phe- 

 nomena of this Norfolk district, which are the abundance of 

 species and individuals of all the freshwater forms ; the paucity 

 of the wood-loving species ; and the great number and variety 

 presented by the hedge-row kinds, as many of the true snails — 

 Helix aspersa, H. nemoralis, H. hortensis, etc. The albinos 

 seem to be fully represented, as this list will show. 



The only former examination of the mollusca of Norfolk 

 was that undertaken in 1872 for the Norfolk and Norwich 

 Natural History Society, by Mr. Jno. B. Bridgman, and was 

 published in the Proceedings of that Society, which still 

 flourishes. 



Mr. Bridgman chiefly collected in the neighbourhood of 

 Norwich. The number of species recorded by him is eighty- 

 four in all. 

 Arion ater (L.). Plentiful on the higher as well as in the marsh 



lands. The black form is usually found, but at Alpington, 



Yelverton, and Rockland, the chocolate-brown shade is 



much the most plentiful (S S.P.) ; St. Faith's, Colney, 



Thorpe, Postwick, and Costessey (A.M.). 

 A. hortensis Fer. Gardens, woods, and waste places, under 



stones and logs of wood. Whitlingham, Yelverton, Fram- 



ingham Earl (S.S.P.) ; Heigham, Earlham, St. Faith's 



(A.M.). 

 Var. grisea. Heigham (A.M.). 

 Amalia sowerbyi (Fer.). A single specimen at Kirby-Bedon 



(AM.). 



.I.e., vii.. July 1S94. 



