Stith Thompson's nearly exhaustive taxonomy of mythical animals in his Motif-Index lists nine sometimes overlapping categories. Another hybrid, the basilisk is a mythical lizard or serpent whose hissing drives other serpents away. Thompson's second major category of mythical animals is "Beast-men", combining bestial and human form. Among the most fabulous of "Mythical birds" is the roc, a giant bird that can carry off people and elephants in its claws. "Mythical fish", as might be expected, abound in Hawaiian, Tahitian, and Tongan mythology. The dragon is a nearly universal motif, a reptilian or snakelike hybrid or compound animal, covered with the scales of a fish and sometimes endowed with claws and wings and the head of an eagle, falcon, or hawk. Celebrated examples in the "Bird-men" category are in fact part women: the sphinx, the harpy, and the siren, as the most popular form of "Fish-men" is the mermaid.