Complex sentence: Mary Horner Lyell (1808--1873) was a conchologist and geologist, and the wife of eminent geologist Charles Lyell, whom she assisted in his scientific work.
Split into simpler sentences: Mary Horner Lyell (1808--1873) was a conchologist and geologist. She was married to the notable British geologist Charles Lyell, and acted as assistant in his scientific work.