Abstract
There is no significant (p⩽0·05) difference in the scratch hardness (Mohs' H = 4±0; mean ±1 S.D.) or indentation hardness (34·87±4·79 kp/mm2) of the teeth of Lytechinus variegatus, Arbacia punctulata, Diadema antillarum, Echinometra lucunter, or Eucidaris tribuloides. The hardness of the teeth of these echinoids gives them the ability to scrape or bore into hard carbonate substrata and to ingest calcareous plants. Differences in form and substructure do not affect the hardness of the teeth of these echinoids.