Two marine animal burrows, perhaps shrimp burrows, in the lower Miocene Topanga Canyon Formation. The animal digs the burrow in which it lives (now filled with the lightest colored sand). Fecal material expelled while the animal is in the burrow is packed against the walls of the burrow to make them smooth (the brown rim around the light colored sand). When the animal permanently leaves the burrow, it fills in with sand. Note that the light colored sand filling the burrow is slightly coarser than the medium brown sand surrounding the burrow.