1. Clawlike, retractile chitinous hooks that encircle or line the rostellum of the scolex of certain taenioid tapeworms for attachment to the intestinal mucosa, with the additional aid of suckers; the hooklets can be withdrawn and the rostellum inverted when the tapeworm moves. Various arrangements and forms of the hooklets characterize the families of taenioid cestodes. 2. Hooklets of degenerated scoleces of Echinococcus species in the fluids of the hydatid cyst. 3. The hooklets of the oncosphere, by which it claws out of its membrane sheath after hatching and penetrates the host gut wall; these hooklets can later be found in the cercomer of the procercoid or cysticercoid.