Scientific Name: Tonna spp. Common Name: Spotted Tun Size: Typically ranges from 10 to 20 cm in length, but can vary depending on the species and individual shell. Shape: Globular or barrel-shaped with a somewhat flattened base. The shell spirals into a wide aperture. Color: Generally creamy or light tan with darker brown spots or streaks. The pattern of spots can vary, giving each shell a unique look.