236 SNAILS AND SLUGS [CH. vn 



Family NERITID^E. Shell globular, thick ; spire small ; aperture 

 semilunate, columellar side expanded ; operculum calcareous 

 with prominences on interior face, one of which articulates with 

 columella. 



genus Neritina Lam. fluviatilis (L.), J", whorls 3, last more than 

 two-thirds of whole shell. Aquatic ; tolerates brackish water. 



Family PALUDESTRINID.E. Shell conical, small, smooth, aperture 

 entire ; an umbilical cleft ; eyes at base of tentacles. Aquatic 

 (brackish). 



genus Paludestrina Orbignj=U^drobia Hartmn. Eyes on tu- 

 bercles. Shell imperforate. Operculum horny. 

 confusa (Frauenfeld), ", whorls 5 or 6. Suture deep ; shell oval, 



stout ; aperture oval ; operculum spiral, not concentric. 

 jenkinsi (Smith), tentacles long, pointed; eyes on dark pro- 

 minences. 

 taylori Smith. 

 ventrosa (Montagu), i", whorls 6 or 7, suture rather deep ; shell 



long and narrow ; aperture oval. 

 stagnalis (Baster), whorls flattened, outer lip simple, inner 



reflected, 

 genus Pseudamnicola Paulucci. Shell perforated, small ; aperture 



oval ; operculum horny, spiral. 



anatina (Drap.). [Identified by Boettger from specimens from 

 Oulton lacking both animal and operculum.] 



Family POMATIIDVE. Shell spiral ; spire elevated ; aperture circular 

 or nearly so ; umbilicus small and narrow. Operculum cal- 

 careous, distinctly spiral. 



genus Pomatias (Studer) = Cyclostoma (Montf.) elegans (Mull), f", 

 shell pale brown with purple tinge ; whorls 4|" ; umbilicus 

 twisted. Beneath stones, dead leaves, in hedgerows, etc. Not 

 found in Scotland. 



Family ASSEMANIID^E. Ocular tubercles long, contractile. Foot 

 short, oval, truncate anteriorly. Shell as in Paludestrinidae. 

 Operculum horny, spiral, 

 genus Assemania Leach. Spire short ; aperture broad, oval, 



entire. Apex near internal edge of aperture. 

 grayana Leach. Estuary of Thames. 



