SPINY structure when it projects out, and BECOMES a circular hollow pit when retracted (taken back). It is STRUCTURALLY composed of a NUMBER of concentric rows of hooks.The Scolex (Head) region of Taenia solium consists of four large suckers and a rostellum containing two rows of large and small hooks.The Scolex of Taenia saginata has four large suckers but lacks rostellum and rostellar hooks. Scolex represents the Head in tapeworm.Suckers: Organs present at the Head region of Tapeworms used for clinging to SURFACES