Dr. Robert N. Margolis, 78, of Woodbridge died Sept. 21. He was the husband of Joan S. Margolis and the widower of Irene Lobenthal.  In addition to his wife, he is survived by his sons, David, Joseph and Tom and two step-daughters, Allison Noel and Valerie Waskow and seven grandchildren. He was also predeceased by his step-son, Mark Noel.