A member of my monthly bug chat group is trying to figure out what this might be and I offered to post it here to get some ideas. It was dug from a hillside in San Pedro, where clams and crabs were also found. My best guess is the formation is Pleistocene Palos Verdes Sand. They have shown it to the ichthyology sections of the LA County Natural History Museum and seem to have ruled out it came from a fish. My best guess is maybe some sort of coprolite? However, its huge and I also wouldn't rule out some sort of human made artifact.