Large scales occur only in three families of batoids. Though they have a wide spectrum of different shapes they all serve protective functions in bottom-dwelling species. The crown consists of enameloid, orthodentine and osteodentine. Three different types of basal plates occur: (a) thin basal plate consisting of acellular bone; (b) basal plate which is secondarily thickened; it consists of massive acellular bone and thin denteons which surround the vascular canals; (c) basal plate which is secondarily thickened, consisting of a peculiar type of microspongy bone which has never been found in other elasmobranchs.