The Collaborative International Dictionary of English v.0.48:

Ray \Ray\, n. [F. raie, L. raia. Cf. Roach.] (Zool.)
   (a) Any one of numerous elasmobranch fishes of the order
       Raiae, including the skates, torpedoes, sawfishes, etc.
   (b) In a restricted sense, any of the broad, flat,
       narrow-tailed species, as the skates and sting rays. See
       Skate.
       [1913 Webster]

   Bishop ray, a yellow-spotted, long-tailed eagle ray
      (Aetobatus narinari syn. Stoasodon narinari) of the
      Southern United States and the West Indies; also called
      the spotted eagle ray and white-spotted eagle ray.

   Butterfly ray, a short-tailed American sting ray
      (Pteroplatea Maclura), having very broad pectoral fins.


   Devil ray. See Sea Devil.

   Eagle ray, any large ray of the family Myliobatidae, or
      Aetobatidae. The common European species (Myliobatis
      aquila) is called also whip ray, and miller.

   Electric ray, or Cramp ray, a torpedo.

   Starry ray, a common European skate (Raia radiata).

   Sting ray, any one of numerous species of rays of the
      family Trygonidae having one or more large, sharp,
      barbed dorsal spines on the whiplike tail. Called also
      stingaree.
      [1913 Webster]

WordNet (r) 3.0 (2006):

devil ray
    n 1: small manta (to 4 feet) that travels in schools [syn:
         devil ray, Mobula hypostoma]