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):

Alosa
    n 1: shad [syn: Alosa, genus Alosa]