Although I would usually respond to such posts privately, since there seem to be quite a few Mendelsohn's, I thought I'd go ahead and respond to the group.
My maternal 2nd g-grandmother was Rebecca Mendelsohn (Rivkah Rikel), born apx 1849 in Warsaw. Her father was Shmuel Mendelzon. I know nothing else about her family and have been unable to find anything.
She married Vitor Moczydlower (in US Mochedlover) in 1872 and immigrated to the US in 1907, where eight of her ten children also ended up.
Northern Arizona, USA
LEVINE/LEWIN, SILBERNAGEL/ZYLBERNAGEL/SILVER, EPSTEJN/EPSTEIN, MOCZYDLOWER/MOCHEDLOVER, ERLICH, GRUNPELTZ, JOSKOWICZ, ZYLBERSZTEJN, SZTABINSKA, WILK