Rays have skeletons of cartilage rather than bone. Cartilage is more flexible and lighter in weight than bone. The skin covering of rays is usually soft and smooth, the they range in color from light to dark grays and brown. Some, like the spotted eagle rays, have a pattern of spots. The underside is usually lighter, a pattern called countershading that is found in many sea creatures and in some birds also.
Most rays have a hard spine on top of the tail.
The spines have serrated edges with sharp points that point back toward the base. Spines can be lost and replaced, and sometimes rays have multiple spines. The spine is used only for defense. A sting mig ht occur, for example, if someone accidentally steps on hidden ray and the animal tries to protect itself. Most rays are bottom-dwellers.