Fig. 



17. N. MONiLiFERA, Lamk. — Nerita glaucina, catena, etc. — Near 



water-mark, in sandy places generally, C. Whorls rounded. 



18. N. SORDIDA, PMl. — N.fulva, plumbea, etc. — Scilly, Cape Clear, 



Zetland, etc., 2.5 to 90 fath., E. 



19. N. PUSiLLA, Sa!/. — N. Grmnlandicajivida, alba. — Northumberland, 



Yorkshire, N. Eu., 4.5 fath., R. White ; umbilicus small. 



Becluzia. 



20. B. APERTA, Jeffreys. — Natka aperta, Loven ? — Zetland, Br. 



Velutina. 



21. N. L«viGATA, Linn. {Helix.) — Bulla, Felutina, etc. — Brit. co. 



generally, 1 to 30 fath., N. Eu., C. 



22. N. FLEXiLis, Mont. {Bulla.) — Coriocella and Sigaretus plicatilis. — 



N. Scot., 25 fath., Br. 



Lamellaru. 



23. L. perspicua, Linn. — Helix, Bulla haliotoidea, Sigareta and Co- 



riocella neritoide'us. — Brit. co. generally, but B. ; 1 to 15 fath., 

 Mr. Thin, glassy, more ventricose than L. tentactdata. 



24. L. tentacdlata, Mont. — Sig. and Cor. — Falmouth, Swansea, Ar- 



ran, etc. Laminarian, Mr. Upper whorls less full than L. per- 

 spicua. 



Otina. 



25. O. OTIS, Turt. {Helix.) — Felutina, Galericulum ovatum. — Wales, 



Devon, Channel Isls., Clare, etc., Mc. Littoral. 



Trichotropis. 



26. T. borealis, Broderip and Sowb. — T. and Murex carinatus, mnbili- 



catiis, acuminatus, etc. — N. Scotland, W. Ireland, 15 to 80 fath., 

 B. 



