What does "houndfish" mean?

Houndfish: Any small shark of the genus Galeus or Mustelus, of which there are several species, as the smooth houndfish (G. canis), of Europe and America; -- called also houndshark, and dogfish. Note: The European nursehound, or small-spotted dogfish, is Scyllium canicula; the rough houndfish, or large-spotted dogfish, is S. catulus. The name has also sometimes been applied to the bluefish (Pomatomus saltatrix), and to the silver gar.