Mollusca of Great Britain. 389 



Testa depressa, utrinque planior, subumbilicata, subtils 



perforata, fragilis, diaphana, politissima, ferrugineo- 



cornea aut albida. AnfractusS — 4; ultimo in carmam 



' acutiusculam utrinque obliquante. Apertura elongata, 



angulata : perist omio non reflexo, columellae insidente. 



Long. 0.05.— Diam. 0.175. 



Planorbis nitidus. Miill. Verm. 2. p. l63. 



complanatus. Drap. Hist, des Moll. p. 45. 



^2./. 20— 22. 

 Helix fontana. Light/, in Phil. Trans. 76. t. 2. f. 1. 



Mont. Test. Brit. p. 462. t. 6.f. 6. 



On aquatic plants in ditches ; but not very common. 



13. LiNEATUS. 



J/zmaZ griseo-fuscum. Tentacula filiformia. (Light/.) 

 Testa supr^ convexa, subtiis planior, perforata, utrinque 

 subumbilicata, fragilis, diaphana, politissima, albido- 

 lutescens. An/ractus 5 — 6 ; ultimo in carinam infe- 

 riorem obtusam utrinque obliquante, septis internis 3 

 vix 4 albis partito. ^per^wra elongata, angulata : pe- 

 ristomio non reflexo, columellae insidente. 



Long. 0.15.— Diam. 0.275. 

 Planorbis nitidus. Drap. Hist, des Moll. p. 46. t. 2. 



/. 17—19? 

 Helix lineata. Walker Test. Min. Bar. 1. 1./. 28. 

 Nautilus lacustris. Light/ in Phil. Trans. 76. t. 1. 

 / 1—7. 

 My specimens were presented to me by Mr. J. S. Miller, 

 and I believe came from the neighbourhood of London. 

 The internal plates seem to stand in the place of the teeth 

 or folds which barricade the apertures of many other Mol- 

 lusca : 



