Encyclopædia Britannica, Ninth Edition/Thornback

THORNBACK is the name given to a species of ray (Raja clavata) which is found all round the coasts of Europe, and locally abundant; it derives its name from the peculiar armature of the skin of its body, the upper and lower surfaces of the body of the female being armed with scattered, more or less numerous, large round osseous bucklers, each with a spine in the centre; the tail also is armed with rows of similar bucklers. In the male fish these bucklers are absent, or nearly so. The thornback does not grow to the same large size as the skates, a specimen three feet across being considered large. It is more valued as food than the other rays, and consumed in large quantities, fresh as well as salted.