The transverse lampshell (Terebratalia transversa) valves or shells are very interesting and different from bivalves like clams. The lampshell has its shells oriented top and bottom, unlike clams and other bivalves that have a left and right side. The bottom shell shows a hole where a stalk (peduncle) comes through to attach to nearby surfaces. This stalk allows the lampshell to remain secure in high current conditions. The transverse lampshell grows to about 3 inches (7.6 cm) across, and has a range from northern Alaska to northern Mexico.