Simplify the following text for a Grade 10 native English-speaking person.
Original: Her primary stock in trade consisted of invertebrate fossils such as ammonite and belemnite shells , which were common in the area and sold for a few shillings .
Simplified: Her stock in trade were invertebrate fossils such as ammonite and belemnite shells , which were common in the area and sold for a few shillings .