The Collaborative International Dictionary of English v.0.48:

Alosa \Alosa\ n.
   the genus comprising the most common varieties of shad. It
   replaces the older term Clupea. See also shad.

   Syn: genus Alosa.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Clupea
    n 1: type genus of the Clupeidae: typical herrings [syn:
         Clupea, genus Clupea]