Pelagia: a lovely, unearthed gem, which I'd consider using, since it honours an ancestor. However, I'd only go with it as a middle name. While it's also Polish, it's extremely dated, and there are about as many Polish girls called
Pelagia as there are English ones called
Ermintrude, and I imagine it'd be mispronounced as "pə-LAY-gee-ə" or "pə-LAY-jee-ə" in English (it's "peh-LA-gya").
Larisa: I like it too. I prefer it spelt (and pronounced)
Larisa in Russia, and
Larissa (rhyming with
Marissa) in English-speaking countries.