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is included in the British Hst on the strength of four probably 

 introduced specimens found in Glamorganshire in 1873 ; while 

 the other two, H. revelata, Mich., and H. pisana, Miill., are 

 restricted to the south-western counties and Channel 

 Islands. The next genus, Bulimus, contains four species, all 

 represented ; though here again, one, B. goodallii, Mull, is an 

 introduced species. Pupa, four species, one absent. Vertigo, 

 eleven species, eight of which are represented, though very 

 locally. Owing to their small size, these shells are very 

 frequently overlooked. Balea, the only species, B. perversa, 

 L., is fairly common. Clausilia, four, all occurring in the 

 district. Cochlicopa, two, C. lubrica, Miill., common everywhere; 

 C /rz^(?;2j-, Pult., rather local. Achatina, Carychiuni, Cyclostoma 

 and Acme, each have their own species represented. It is 

 possible and probable that before the list is completed some 

 of these vacancies may be filled up, but this is how it stands 

 at the present time. 



The divisions which I have marked out here are not 

 intended to be arbitrary, or rigidly defined, but merely to show 

 how certain districts are characterised by the presence of 

 certain shells. For example, anyone wishing to procure 

 specimens of the large Roman snail. Helix pomatia, would 

 naturally go to the chalk downs, and would never think of 

 wasting his time looking over heath or sandy country ; and in 

 the same way we go to stagnant ditches or marsh-land for 

 Limncea glutinosa, Miill., running water or lakes for Unios ; 

 quiet pools for the large Anodontas ; and muddy waters and 

 canals for the large Limnceas ; while other species like H. 

 carthusiana, Miill., and Bulimus acutus, Miill., are known never 

 to occur more than a mile or two inland. Broadly speaking, 

 the chalk district supports the largest and most varied 

 molluscan fauna ; next in order comes the low-lying alluvial 

 land ; while the poorest districts are the dry heath and sandy 

 country or districts of woods, as Virginia Water, Bagshot, or 

 Leith Hill. In these and similar places shells are few in 

 number ; there is less variety, and their texture is sometimes 

 exceedingly thin. Granite and peat are the most unfavourable 

 to mollusca ; but we are not troubled much with either of 

 these in our district. 



Dr. Gwyn Jeffreys, who was perhaps our best authority, 



