The ground sharks (Carcharhiniformes) are an order of cartilaginous fish which includes the hammerhead sharks, cat sharks and requiem sharks.
This is the biggest order of sharks, and they are found in marine, brackish and freshwater.
Only species are recorded in Hebridean waters the Lesser-spotted Dogfish and the Nursehound.
Ground sharks have a wide mouth with sharp-edged teeth and a moveable membrane over their eyes to protect them when they are feeding. Reef sharks and the flat headed hammerheads belong to this order. There are eight families in this order and 50 genera, all have five gills, anal fins and two dorsal fins.