PLATE XIL 



Ianthina. Floats on ocean. 

 Fig. 

 1. I. communis, Land. — Helix Ianthina, Lfragilis, etc. — Cornwall, 



Bristol, etc. ; oceanic, 0. Sides depressed. 

 8. I. britannica, Leech. Beeve. — Ireland, Cornwall, etc, Mr. 



Darkly coloured, not compressed. 



3. I. pallida, Harvey. — I. patula. — Clare, Rr. as Brit. 



4. I. exigua, Lamk, — Cornwall, Clare, etc., Mr. 



Neritina. In rivers. 



5. N. fluviatilis, Linn. — N.fontimlis. — Thames, Trent, Huinbcr, 



etc., Scotch lakes, Cc. 



Bithinia. In ponds. 



6. B. Leachii, Shepp. (Turbo.) — B. ventricosus, Paludina acuta, simu 



lis, etc. — Rivers S. Brit., Mr. Narrow, with rounded whorls. 



7. B. TENTACULATA,Zmw. (Helix.) — T. nucleus, Paludina impura, etc. 



— Fresh-water, throughout Brit. Oval. 



Paludina. In ponds. 



8. P. Listeri, Forbes and Hanley. — Helix vivipara, etc. — Lakes and 



ponds generally, Mc. Whorls more separate, umbilicus larger 

 than P. vivipara. 



9. P. vivipara, Linn. — Pal. achatma, etc.— Thames, etc., C. 



Valvata. In ponds. 



10. V. pisoinalis, Miiller. — Nerita, Turbo, Cyclostoma fontmaUs, ob- 



tusa, thermalis, etc. — Fresh-water, C. Subglobose. 



11. V. cristata, Miiller. — V. planorbis, etc. — Many loc, Mc. Or- 



bicular. 



Littorina. On the sea-shore. 



12. 13. L. rudis, Bonov. (Turbo.) — L. littoreus, etc., L. nigro-Uneatus 



(var. f. 13). — British shores generally, Cc. 

 14, 15. L. littorea, Linn. (Turbo.) — L. vulgaris, etc. — British shores 



generally. The common eatable "Winkle. 

 16, 17. L. tenebrosa, Mont. (Turbo). — British shores generally, C. 



Not thickened at bottom of mouth like L. rudis, 

 18. L. patula, Jeffreys. — L. labiata, L. jugosa, etc. — Common on 



our shores. 



