I think my reasoning goes that in french, a trailing s denotes a plural much more regularly than in english (or so it seems to me, I have no way to measure this

I think my reasoning goes that in french, a trailing s denotes a plural much more regularly than in english (or so it seems to me, I have no way to measure this in a serious way). I know the grammar rule that says that "James's bicycle" is not correct, "James' bicycle" is (and I seem to remember that the only reason is that a double s cannot be pronounced) Combine these two facts and you've got "no s as possessive at the end of a plural" rule that formed in my tired mind :-)