This may be old news for some, but I've found several articles which
explain why N. lapillus is declining or extinct from Norway.  A
xenobiotic, tributyltin (TBT), used as a biocide in boat antifouling
paints and also in paper and textile mills as well as breweries
contaminates waters and has been found to be the cause of sterilization in
many species including N. lapillus, N. lamellosa, N. lima, Urosalpinx
cinerea, Ocenebra erinacea, Hinia reticulata, Trivia arctica and Trivia
monacha.