Cross.section of skin bone (aceliular.nonflexible) ganoine (enamel) sca日 dermis Ganoid bone (acellular.fiexible) enamel (not ganoine) mucus gland epldermls 3 穷 cycloid scale dermis ctenoid 子r1HIT1 B.Bony ridge scale pulp cavity 口ermis C.Placoid