HELEN SELENA (SHERIDAN), COUNTESS OF (1807-1867).-Eldest _dau._ of Tom S., grand-daughter of Richard Brinsley S. (_q.v._), and sister of Mrs. Norton (_q.v._). She and her two sisters were known as "the three Graces," the third being the Duchess of Somerset. She shared in the family talent, and wrote a good deal of verse, her best kno