many of the species are brilliantly coloured. The common European species (Coracias garrula) has the head, neck, and under parts light blue varied with green, the scapulars chestnut brown, and the e4e
tail blue, green, and black. The broad-billed rollers of india and Africa belong to the genus Eurystomus, as the oriental roller (E. Orientalis), and the Australian roller, or dollar bird (E. Pacificus). The latter is dark brown on the head and neck, sea green on the back, and bright blue on the throat, base of the tail, and parts of the wings. It has a silvery-white spot on the middle of each wing.
(Science: zoology) ground roller, any one of several species of madagascar rollers belonging to Atelornis and allied genera. They are nocturnal birds, and feed on the ground. Roller bolt, the bar in a carriage to which the traces are attached; a whiffletree. Roller gin, a cotton gin inn which rolls are used for separating the seeds from the fibre. Roller mill. See Mill. Roller skate, a skate which has small wheels in the place of the metallic runner; designed for use in skating upon a smooth, hard surface, other than ice.