Musculature of the pharynx, introvert and mouth cone in Echinoderes . Confocal z-stack projections of phalloidin staining within the pharynx at different degrees of retraction. Ventral views, with anterior to the top in all images. (A-C) Echinoderes dujardinii. (D-F) Echinoderes spinifurca. In each micrograph, there are distinct muscle fibers connecting with, and enclosing, the pharyngeal bulb, including protractors, retractors, suspensors, and fibers of the pharynx sheath. An asterisk marks a muscle connecting the pharynx with the mouth cone external circular muscle. Abbreviations: esm, esophagus muscles; icm, introvert circular muscle; icmr, introvert circular muscle retractors; idr, introvert distal retractor; ipr, introvert proximal retractor; ir, introvert retractor; mce, mouth cone external circular muscle; mci, mouth cone internal circular muscle; ncm, neck circular muscle; osm, outer oral style muscle; pb, pharynx bulb; phs, pharynx suspensor; pip, pharynx internal protractor; pms, pharynx muscular sheath; pop, pharynx outer protractor; prm, pharynx retractor muscles; sph, sphincter. Scale bar, 20 μm.