A small shark, of many species, of the genera Mustelus, Scyllium, Spinax, etc. 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.