The Collaborative International Dictionary of English v.0.48:

Houndfish \Hound"fish\, n. (Zool.)
   Any small shark of the genus Galeus or Mustelus, of which
   there are several species, as the smooth houndfish (Galeus
   canis), of Europe and America; -- called also houndshark,
   and dogfish.
   [1913 Webster]

   Note: The European nursehound, or small-spotted dogfish, is
         Scyllium canicula; the rough houndfish, or
         large-spotted dogfish, is Scyllium catulus. The name
         has also sometimes been applied to the bluefish
         (Pomatomus saltatrix), and to the silver gar.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Roussette \Rous*sette"\, n. [F.; -- so called in allusion to the
   color. See Russet.]
   1. (Zool.) A fruit bat, especially the large species
      (Pieropus vulgaris) inhabiting the islands of the Indian
      ocean. It measures about a yard across the expanded wings.
      [1913 Webster]

   2. (Zool.) Any small shark of the genus Scyllium; -- called
      also dogfish. See Dogfish.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Amia \Am"i*a\, n. [L., fr. Gr. ? a kind of tunny.] (Zool.)
   A genus of fresh-water ganoid fishes, exclusively confined to
   North America; called bowfin in Lake Champlain, dogfish
   in Lake Erie, and mudfish in South Carolina, etc. See
   Bowfin.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dogfish \Dog"fish`\, n. (Zool.)
   1. A small shark, of many species, of the genera Mustelus,
      Scyllium, Spinax, etc.
      [1913 Webster]

   Note: The European spotted dogfishes (Scyllium catudus, and
         Scyllium canicula) are very abundant; the American
         smooth, or blue dogfish is Mustelus canis; the common
         picked, or horned dogfish (Squalus acanthias)
         abundant on both sides of the Atlantic.
         [1913 Webster]

   2. The bowfin (Amia calva). See Bowfin.
      [1913 Webster]

   3. The burbot of Lake Erie.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bowfin \Bow"fin`\, n. (Zool.)
   A voracious ganoid fish (Amia calva) found in the fresh
   waters of the United States; the mudfish; -- called also
   Johnny Grindle, and dogfish.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dogfish
    n 1: primitive long-bodied carnivorous freshwater fish with a
         very long dorsal fin; found in sluggish waters of North
         America [syn: bowfin, grindle, dogfish, Amia calva]
    2: any of several small sharks