Guessing these might be Chinese beads, I did a quick zoom through PandaHall and found a couple of possible candidates. There may be more lurking...PandaHall is one of those place you can sink out of sight fast.

http://www.pandahall.com/p-533861-shell-beads-strands-white-10x5mm.html?areaType=NormalArea

http://www.pandahall.com/p-533883-shell-beads-strands-white-9x4mm.html?areaType=NormalArea

http://www.pandahall.com/p-630436-shell-beads-strands-white-about-10mm-long.html?areaType=NormalArea