ClipArt ETC
"Diagram of an Echinus (stripped of its spines). a, mouth; a', gullet; b, teeth; c, lips; d, alveoli; e, falces; f, f, auriculariae; g, retractor, and h, protractor, muscles of Aristotle's lantern; i, madreporic canal; k, circular ambulacral vessel; l, Polian pedicels; r, r, spines; s, tubercle; s', tubercle to which a spine is articulated; t, t, pedicellariae; u, anus; v, madreporic tubercle; x, ocular spot." -Whitney, 1911

Sea Urchin Section

"Diagram of an Echinus (stripped of its spines). a, mouth; a', gullet; b, teeth; c, lips; d, alveoli;…