From Sarah Corbett on the Ethnic Jewels Community on Facebook...

"I have some history on these mysterious beads! Made by one nomadic family in Mauritania called Lmalem . They travelled between Boutelamin, Kiffa and Nouakchott making these carved beads for the weddings of high status B'than Maure families. The family would supply the beads and have them carved. Originally done with Amber beads, but those would break, so since 1940 only French Amber ( Bakelite) was used. Name in Mauritania is Muhafen Luban. Meaning improved Amber. (source of the information is a Mauritanian friend from the region)"

Here, Rosanna's post from last summer's Picard Museum trip:

http://beadcollector.net/cgi-bin/anyboard.cgi?fvp=/openforum/&cmd=get&cG=336363838343&zu=333636383539&v=2&gV=0&p=

and her image copied below.