This is a bivalve fossil, a gift, so the origin and species are unknown. I would appreciate it if someone knowledgeable could confirm it from the photos provided. The main body measures approximately 8 cm along its longest axis and 6 cm along its shortest axis, with a thickness of about 6 cm. The total weight, including the matrix, is about 160g. The matrix appears to be Tertiary mudstone, not very consolidated; it is soft enough to be scratched with a fingernail and leaves soil particles on your hands when touched. It is quite old, and the entire piece has a slight oily odor. The surface is divided into light and dark colored areas. For this listing, I have removed as much of the matrix as possible without damaging the fossil. I kindly request consideration from those who are interested.