The answer with no clasp is = 5040.....the reason why is the we have a circle where the position of one of the shells is "set"......so we can arrange the others in 7! ways
With a clasp the answer is 40320, since when the clasp is undone and the braclet is laid out in a linear fashion, we have 8 ways to choose which shell goes first in the chain, 7 ways to choose the second, etc.
