Oral region with the lantern of Aristotle in formation.

Aboral surface (opposite to mouth).

Remnants of the larval skeleton in the aboral region of the juvenile.

Aboral surface (opposite to mouth).

Structure in the anal region.

Ossicles of the lantern of Aristotle in formation at the oral region.

Early stage with two arms (post-oral).

Ossicles of the lantern of Aristotle in formation at the oral region.

Structure in the anal region.

Four-arm stage with a vestibule invagination.

Polarized light highlights the calcareous skeleton showing the structure of spines, podia, and remnants of the larval skeleton.

Detail of teeth in the lantern of Aristotle.

Frontal view of the eight-arm pluteus larva.

Four-arm stage.

Mouth, esophagus, gut and vestibule invagination (larva left side) during six-arm stage. Anal view.

Epithelium.

Vestibule invagination in a four-arm pluteus larva.

Detail of the vestibule near the left coelom and the central gut during early eight-arm stage.

Advanced stage with the archenteron near the apical plate.

Ambulacral feet and spines.

Arm growing on an unusual site.

Stage with four pairs of arms.